Resist composition and patterning process

ABSTRACT

A resist composition comprises a polymer comprising recurring units having formula (1) wherein R 1 , R 4 , R 7 , and R 14  are H or methyl, R 2 , R 3 , R 15 , and R 16  are H, alkyl or fluoroalkyl, R is F or H, R 5  is alkylene, R 6  is fluorinated alkyl, R 8  is a single bond or alkylene, R 10  and R 11  are H, F, methyl or trifluoromethyl, R 12  and R 13  are a single bond, —O— or —CR 18 R 19 —, R 9 , R 18 , and R 19  are H, F, methyl or trifluoromethyl, R 17  is alkylene, X 1 , X 2  and X 3  are —C(═O)—O—, —O—, or —C(═O)—R 20 —C(═O)—O— wherein R 20  is alkylene, 0≦(a-1)&lt;1, 0≦(a-2)&lt;1, 0≦(a-3)&lt;1, 0&lt;(a-1)+(a-2)+(a-3)&lt;1, 0&lt;b&lt;1, and 0&lt;(a-1)+(a-2)+(a-3)+b≦1.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application No. 2006-282203 filed in Japan on Oct. 17, 2006,the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to resist compositions for use in the lithographytechnology for the microfabrication of semiconductor devices or thelike, especially the immersion photolithography utilizing an ArF excimerlaser of wavelength 193 nm as the light source and interposing waterbetween a projection lens and a wafer. It also relates to a patterningprocess using the resist compositions.

BACKGROUND ART

In the recent drive for higher integration and operating speeds in LSIdevices, the pattern rule is made drastically finer. Thephotolithography which is currently on widespread use in the art isapproaching the essential limit of resolution determined by thewavelength of a light source.

As the light source used in the lithography for resist patternformation, g-line (436 nm) or i-line (365 nm) from a mercury lamp waswidely used. One means believed effective for further reducing thefeature size is to reduce the wavelength of exposure light. For the massproduction process of 64 MB dynamic random access memories (DRAM,processing feature size 0.25 μm or less) and later ones, the exposurelight source of i-line (365 nm) was replaced by a KrF excimer laserhaving a shorter wavelength of 248 nm.

However, for the fabrication of DRAM with a degree of integration of 256MB and 1 GB or more requiring a finer patterning technology (processingfeature size 0.2 μm or less), a shorter wavelength light source isrequired. Over a decade, photolithography using ArF excimer laser light(193 nm) has been under active investigation.

It was expected at the initial that the ArF lithography would be appliedto the fabrication of 180-nm node devices. However, the KrF excimerlithography survived to the mass-scale fabrication of 130-nm nodedevices. So, the full application of ArF lithography started from the90-nm node. The ArF lithography combined with a lens having an increasednumerical aperture (NA) of 0.9 is considered to comply with 65-nm nodedevices.

For the next 45-nm node devices which required an advancement to reducethe wavelength of exposure light, the F₂ lithography of 157 nmwavelength became a candidate. However, for the reasons that theprojection lens uses a large amount of expensive CaF₂ single crystal,the scanner thus becomes expensive, hard pellicles are introduced due tothe extremely low durability of soft pellicles, the optical system mustbe accordingly altered, and the etch resistance of resist is low; thepostponement of F, lithography and the early introduction of ArFimmersion lithography were advocated (see Proc. SPIE Vol. 4690 xxix).

In the ArF immersion lithography, the space between the projection lensand the wafer is filled with water. Since water has a refractive indexof 1.44 at 193 nm, pattern formation is possible even using a lens withNA of 1.0 or greater. Theoretically, it is possible to increase the NAto 1.35. The resolution is improved by an increment of NA. A combinationof a lens having NA of at least 1.2 with ultra-high resolutiontechnology suggests a way to the 45-nm node (see Proc. SPIE Vol. 5040, p724).

Several problems associated with the presence of water on resist werepointed out. Because the photoacid generator in the resist film, theacid generated therefrom upon exposure, and the amine compound added tothe resist as a quencher can be leached in water in contact with theresist film, pattern profile changes occur. The pattern collapses due toswelling of the resist film with water.

With respect to the leaching of resist components into water, a studystarted from the standpoint of preventing the projection lens of thelithography system from contamination. Several lithography systemmanufacturers proposed the limit of leach-outs.

For overcoming these problems, it was proposed to provide a protectivecoating of perfluoroalkyl compound between the resist film and water(see the 2nd Immersion Workshop, Jul. 11, 2003, Resist and CoverMaterial Investigation for Immersion Lithography). The provision of sucha protective coating avoids direct contact between the resist film andwater and inhibits the resist film from being leached with water.

However, protective coatings made of perfluoroalkyl compounds usefluorocarbons like Freon® as the diluent for controlling a coatingthickness. As is well known, the use of fluorocarbons is a considerationin view of environmental protection. In addition, the protective coatingmust be stripped prior to development of the resist film. Therefore,special units for coating and stripping of the protective film must beadded to the existing system. Fluorocarbon solvents add to the expense.These factors raise serious problems on practical use.

One means proposed for mitigating practical drawbacks of the protectivefilm of solvent stripping type is a protective film of the type which issoluble in alkaline developer (JP-A 2005-264131). The alkali-solubleprotective film is epoch-making in that it eliminates a need for astripping step or a special stripping unit because it can be strippedoff at the same time as the development of a photoresist film. However,on use of a protective film of alkaline developer soluble type, the stepof coating a protective film is still necessary. Also, the diluentsolvent necessary to form a coating solution of protective film materialmust be selected from those solvents in which the photoresist film isnot readily dissolved, because the solvent should not attack theunderlying film or photoresist film. To avoid troubles like resinprecipitation resulting from mixing of the resist and protective filmcoating solutions, a special unit for coating of a protective film isneeded.

As discussed above, the immersion lithography suffers from drawbacksincluding an increased cost due to use of a protective film. One efforttaken to overcome these problems is the development of a resistcomposition for the immersion lithography which is endowed with abarrier property against water and thus eliminates a need for protectivefilm. This will achieve a cost reduction as well.

The ArF immersion lithography systems commercially available at thepresent are designed such that water is partly held between theprojection lens and the wafer rather than immersing the resist-coatedsubstrate fully in water, and exposure is carried out by scanning thewafer-holding stage at a speed of 300 to 550 mm/sec. Because of suchhigh-speed scanning, water cannot be held between the projection lensand the wafer, and water droplets are left on the surface of the resistfilm or protective film after scanning. It is believed that residualdroplets cause defective pattern formation.

To eliminate the droplets remaining on the surface of the resist orprotective film after scanning, it is necessary to improve the flow ormobility of water on the relevant coating film. It is reported that thenumber of defects associated with the immersion lithography can bereduced by increasing the receding contact angle of the resist orprotective film with water. See 2nd International Symposium on ImmersionLithography, 12-15 Sep., 2005, Defectivity data taken with a full-fieldimmersion exposure tool, Nakano et al.

However, no compromise has been established between barrier property andreceding contact angle. There is a need for a resist composition capableof meeting both the requirements.

Resist compositions for mask blanks suffer from problems including achange of sensitivity during long-term exposure in vacuum and long-termstability after coating. With respect to the stability in vacuum, animprovement is made by a combination of acid labile groups of acetal andtertiary ester types (U.S. Pat. No. 6,869,744). It is believed thatafter coating of a resist composition, an amine component is adsorbed tothe resist film surface whereby the resist varies its sensitivity orprofile. A method of preventing adsorption of an amine component orsurface modification of the resist film is believed effective forimproving the stability after coating.

It is reported that the profile of a line-and-space pattern differsbetween a bright pattern where a peripheral portion around the patternis exposed and a dark pattern where a peripheral portion around thepattern is not exposed. When a peripheral portion around the pattern isexposed, the acid generated in the peripheral portion can evaporateduring PEB to cover the pattern area, whereby the line pattern undergoesa film slimming. When a peripheral portion around the pattern is notexposed, no acid is supplied from the peripheral portion and inversely,amine evaporates whereby the line pattern takes a bulged top profile.This difference of profile, which is referred to as “dark-brightdifference,” occurs in the immersion lithography, but a similarphenomenon also occurs in dry lithography and electron beam vacuumlithography. The dark-bright difference can be reduced by providing aprotective coating on the resist film.

DISCLOSURE OF THE INVENTION

An object of the invention is to provide a resist composition whichforms a resist film having good barrier property against water,effective for preventing leaching with water, and having a high recedingcontact angle with water enough to eliminate residual droplets without aneed for a protective coating, and which has improved processadaptability for use in the immersion lithography. Another object is toprovide a patterning process using the resist composition.

Making experimentation to attain the above and other objects, theinventors have arrived at the following discovery.

JP-A 2005-232095 discloses a methacrylate ester having both a bulkyalkyl group and a hexafluoroalcohol group. A homopolymer of this esterhas a very high water repellency, but is insoluble in alkali, with arisk that when added to a resist composition, it can cause defects afterdevelopment. Then, by copolymerizing with alkali-soluble units for usein resist protective coatings as described in JP-A 2006-145777, JP-A2007-25634, and Japanese Patent Application No. 2007-012135, a materialcapable of meeting both water repellency and alkali solubility wasdeveloped. This material, however, is suited for forming a protectivecoating on a resist film in the immersion lithography.

The present invention provides a resist composition comprising a polymercomprising recurring units having the general formula (I).

Herein R¹, R⁴, R⁷, and R¹⁴ are each independently hydrogen or methyl;R², R³, R¹⁵, and R¹⁶ are each independently hydrogen or a straight,branched or cyclic C₁-C₂₀ alkyl or fluoroalkyl group, or R² and R³, andR¹⁵ and R¹⁶ may bond together to form a ring with the carbon atom towhich they are attached, and in this case, R² and R³, and R¹⁵ and R¹⁶,taken together, stand for a straight, branched or cyclic C₂-C₂₀ alkyleneor fluoroalkylene group; R is fluorine or hydrogen, or may bond with R⁵to form a ring of 3 to 10 carbon atoms in total with the carbon atom towhich they are attached; R⁵ is a straight, branched or cyclic C₁-C₆alkylene group in which at least one hydrogen atom may be substituted bya fluorine atom; R⁶ is a straight or branched C₁-C₁₀ alkyl group inwhich at least one hydrogen atom is substituted by a fluorine atom, R⁵and R⁶ may bond together to form a ring with the carbon atoms to whichthey are attached, and in this case, R⁵ and R⁶, taken together, standfor a trivalent organic group of 2 to 12 carbon atoms in total in whichat least one hydrogen atom is substituted by a fluorine atom; R⁸ is asingle bond or a C₁-C₄ alkylene group; R¹⁰ and R¹¹ are eachindependently hydrogen, fluorine, methyl or trifluoromethyl; R¹² and R¹³are each independently a single bond, —O— or —CR¹⁸R¹⁹—; R⁹, R¹⁸, and R¹⁹are hydrogen, fluorine, methyl or trifluoromethyl; R¹⁷ is a straight orbranched C₁-C₄ alkylene group or may bond with R¹⁵ or R¹⁶ to form aC₃-C₁₀ aliphatic ring with the carbon atom to which they are attached;X¹, X² and X³ are each independently —C(═O)—O—, —O—, or—C(═O)—R²⁰—C(═O)—O— wherein R²⁰ is a straight, branched or cyclic C₁-C₁₀alkylene group; the subscripts are numbers in the range: 0≦(a-1)<1,0≦(a-2)<1, 0≦(a-3)<1, 0<(a-1)+(a-2)+(a-3)<1, 0<b<1, and0<(a-1)+(a-2)+(a-3)+b≦1.

The resist composition forms a resist film which has good barrierproperty against water so that leaching of the resist film with water iscontrolled during the immersion lithography. Then a change of patternprofile due to leach-out is minimized. Thus the invention eliminates aneed for a protective coating which is otherwise used in the immersionlithography for preventing leaching, and reduces the cost required forformation of a protective coating. Additionally, the resist film has sohigh a receding contact angle with water that few droplets are left onthe resist film after the scanning step of the immersion lithography.This minimizes defective pattern formation caused by droplets remainingon the film surface. Therefore, the resist composition of the inventionhas process adaptability, and can form a microscopic pattern with fewdefects at a high precision by the immersion lithography while reducingthe cost.

In a preferred embodiment, the resist composition is a chemicallyamplified resist composition which may be either positive or negative.Preferably the chemically amplified positive resist composition maycomprise a base resin comprising at least recurring units having acidlabile groups and recurring units having hydroxy groups and/or adhesivegroups of lactone ring.

Where the base resin includes recurring units having hydroxy groupsand/or adhesive groups of lactone ring, the chemically amplifiedpositive resist composition ensures tight adhesion to a substrate. Wherethe base resin includes recurring units having acid labile groups, theacid labile groups are deprotected with the acid generated by the acidgenerator during exposure so that the exposed area of resist isconverted to be soluble in a developer, ensuring that a pattern isformed at a very high precision.

Also preferably the resist composition further comprises at least onemember selected from among an organic solvent, a basic compound, adissolution regulator, and a surfactant.

The inclusion of an organic solvent can facilitate to coat the resistcomposition to substrates or the like. The inclusion of a basic compoundcan hold down the diffusion rate of acid within the resist film, leadingto a further improved resolution. The inclusion of a dissolutionregulator can increase the difference in dissolution rate betweenexposed and unexposed areas, leading to a further improved resolution.The addition of a surfactant can further facilitate or control thecoating operation of the resist composition.

In another aspect, the invention provides a pattern forming processcomprising the steps of applying the aforementioned resist compositiononto a substrate to form a coating, heat treating the coating andexposing it to high-energy radiation, and developing the exposed coatingwith a developer. The step of heat treatment may be included after theexposing step and before the developing step. The process may furtherinclude subsequent steps such as etching, resist removal and cleaning.

Preferably the high-energy radiation has a wavelength of 180 to 250 nm.The exposure using high-energy radiation with a wavelength of 180 to 250nm enables to form a finer pattern.

In preferred embodiments, the exposing step is by immersion lithographyinvolving exposing the coating to high-energy radiation through aliquid. The immersion lithography may involve using high-energyradiation having a wavelength of 180 to 250 nm, introducing a liquidbetween the resist-coated substrate and a projection lens, and exposingthe substrate to the high-energy radiation through the liquid. By theimmersion lithography, the resolution is improved and a finer pattern isformed. The liquid is typically water. The high-energy radiation may bean electron beam.

An embodiment of exposure using electron beam is a pattern formingprocess comprising the steps of applying the aforementioned resistcomposition onto a mask blank substrate to form a coating, heat treatingthe coating and exposing it to high-energy radiation, and developing thecoating with a developer.

BENEFITS OF THE INVENTION

The resist film formed from the inventive resist composition has goodbarrier property against water so that leaching of the resist film withwater is controlled. Then a change of pattern profile due to leach-outis minimized. Thus the invention eliminates a need for a protectivecoating which is otherwise used in the immersion lithography forpreventing leaching, and reduces the cost required for formation of aprotective coating.

The resist film formed from the inventive resist composition has theadvantage that if the surface of the resist film is covered with a filmwhich is stable to acids and amines and alkali soluble, for suppressingevaporation of acids and amines during dry lithography, then thedifference in profile and size between bright and dark patterns(dark-bright difference) is reduced in the dry lithography as in thecase of immersion lithography. In addition, the stability of size duringexposure in vacuum, typically during electron beam exposure is improved.

Additionally, the resist film has so high a receding contact angle withwater that few droplets are left on the resist film after the scanningstep of the immersion lithography. This minimizes defective patternformation caused by droplets remaining on the film surface. Therefore,the resist composition of the invention can form a microscopic patternwith minimal defects at a high precision by the immersion lithographywhile reducing the cost.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The terms “a” and “an” herein do not denote a limitation of quantity,but rather denote the presence of at least one of the referenced item.

As used herein, the notation (C_(n)-C_(m)) means a group containing fromn to m carbon atoms per group.

With respect to the immersion lithography, it would be desirable to havea resist composition having both barrier property and a high recedingcontact angle. In connection with the immersion lithography whereinwater is in direct contact with the resist film in the absence of aprotective coating, the inventors have found that when a specificpolymeric additive is incorporated in a resist film, the additive iseffective (i) for preventing the resulting resist film from beingleached with water and (ii) for increasing the receding contact angle ofthe resist film with water. Elaborating the composition and compoundingof a polymeric additive, the inventors have completed the invention.

Polymer

The first embodiment of the invention is a resist composition comprisinga polymer comprising recurring units having the general formula (I).

Herein R¹, R⁴, R⁷, and R¹⁴ are each independently hydrogen or methyl,R², R³, R¹⁵, and R¹⁶ are each independently hydrogen or a straight,branched or cyclic C₁-C₂₀ alkyl or fluoroalkyl group, or R² and R³, andR¹⁵ and R¹⁶ may bond together to form a ring with the carbon atom towhich they are attached, and in this case, R² and R³, and R¹⁵ and R¹⁶,taken together, stand for a straight, branched or cyclic C₂-C₂₀ alkyleneor fluoroalkylene group, R is fluorine or hydrogen, or may bond with R⁵to form a ring of 3 to 10 carbon atoms in total with the carbon atom towhich they are attached.

R⁵ is a straight, branched or cyclic C₁-C₆ alkylene group in which atleast one hydrogen atom may be substituted by a fluorine atom, R⁶ is astraight or branched C₁-C₁₀ alkyl group in which at least one hydrogenatom is substituted by a fluorine atom, R⁵ and R⁶ may bond together toform a ring with the carbon atoms to which they are attached, and inthis case, R⁵ and R⁶, taken together, stand for a trivalent organicgroup, specifically hydrocarbon group of 2 to 12 carbon atoms in totalin which at least one hydrogen atom is substituted by a fluorine atom.

R⁸ is a single bond or a C₁-C₄ alkylene group, R¹⁰ and R¹¹ are eachindependently hydrogen, fluorine, methyl or trifluoromethyl, R¹² and R¹³are each independently a single bond, —O— or —CR¹⁸R¹⁹—, R⁹, R¹⁸, and R¹⁹are hydrogen, fluorine, methyl or trifluoromethyl.

R¹⁷ is a straight or branched C₁-C₄ alkylene group or may bond with R¹⁵or R¹⁶ to form a C₃-C₁₀ aliphatic ring with the carbon atom to whichthey are attached.

X¹, X² and X³ are each independently —C(═O)—O—, —O—, or—C(═O)—R²⁰—C(═O)—O— wherein R²⁰ is a straight, branched or cyclic C₁-C₁₀alkylene group.

The subscripts are numbers in the range: 0≦(a-1)<1, 0≦(a-2)<1,0≦(a-3)<1, 0<(a-1)+(a-2)+(a-3)<1, 0<b<1, and 0<(a-1)+(a-2)+(a-3)+b≦1.

The resist film formed from the resist composition having added theretothe polymer comprising recurring units of formula (I) has good barrierproperty against water so that leaching of the resist film with waterduring immersion lithography is controlled. Then a change of patternprofile due to leach-out is minimized. This eliminates a need for aprotective coating which is otherwise used in the immersion lithographyfor preventing leaching, and reduces the cost required for formation ofa protective coating.

Additionally, the resist film has so high a receding contact angle withwater during scanning exposure that few droplets are left on the resistfilm after the scanning step of the immersion lithography. Thisminimizes defective pattern formation caused by droplets remaining onthe film surface. Therefore, the resist composition of the invention canform a microscopic pattern with minimal defects at a high precision bythe immersion lithography while reducing the cost.

Examples of recurring units (a-1) in formula (I) are given below, butnot limited thereto.

Herein R¹ is as defined above.

Examples of recurring units (a-2) in formula (I) are given below, butnot limited thereto.

Herein R⁴ is as defined above.

Examples of recurring units (a-3) in formula (I) are given below, butnot limited thereto.

Herein R⁷ is as defined above.

Examples of recurring units (b) in formula (I) are given below, but notlimited thereto.

Herein R¹⁴ is as defined above.

Desirably the polymer comprising recurring units of formula (1) has aweight average molecular weight (Mw) of about 1,000 to about 100,000,and especially about 3,000 to about 30,000, as determined by gelpermeation chromatography (GPC) using polystyrene standards. The Mw ofthe polymer is not limited thereto. A polymer with Mw of at least 1,000exerts sufficient barrier property against water during immersionlithography and is effective for preventing the resist film from beingleached with water. A polymer with Mw of up to 100,000 has asufficiently high rate of dissolution in an alkaline developer,minimizing the risk that when a resist film having the polymerincorporated therein is patterned, resin residues are left attached tothe substrate.

When used in the resist composition, the polymers comprising recurringunits of formula (I) may be compounded alone or as a mixture of two ormore polymers in any desired proportion.

The subscripts (a-1), (a-2), (a-3), and (b) representative ofcopolymerization ratios (on a molar basis) of the corresponding unitsare in the range:

0≦(a-1)<1, 0≦(a-2)<1, 0≦(a-3)<1, 0<(a-1)+(a-2)+(a-3)<1, 0<b<1, and0<(a-1)+(a-2)+(a-3)+b≦1,

preferably 0≦(a-1)≦0.95, 0≦(a-2)≦0.95, 0≦(a-3)≦0.95,0.1≦(a-1)+(a-2)+(a-3)≦0.95, 0.05≦b≦0.95, and 0.1≦(a-1)+(a-2)+(a-3)+b≦1,and

more preferably 0≦(a-1)≦0.9, 0≦(a-2)≦0.9, 0≦(a-3)≦0.9,0.1≦(a-1)+(a-2)+(a-3)≦0.9, 0.1≦b≦0.9, and 0.2≦(a-1)+(a-2)+(a-3)+b≦1.

It is noted that the meaning of (a-1)+(a-2)+(a-3)+b=1 is that in apolymer comprising recurring units (a-1), (a-2), (a-3), and (b), the sumof recurring units (a-1), (a-2), (a-3) and (b) is 100 mol % based on thetotal amount of entire recurring units. The meaning of(a-1)+(a-2)+(a-3)+b<1 is that the sum of recurring units (a-1), (a-2),(a-3), and (b) is less than 100 mol % based on the total amount ofentire recurring units, indicating the inclusion of other recurringunits. Examples of the other recurring units include those derived fromvinyl ethers, norbornadienes, maleimides, and vinylsulfones.

In the resist composition of the invention, the polymer(s) may becompounded in a total amount of 0.1 to 50 parts by weight, andpreferably 0.5 to 10 parts by weight per 100 parts by weight of the baseresin. At least 0.1 phr of the polymer is effective in improving thereceding contact angle with water of the photoresist film at itssurface. Up to 50 phr of the polymer is effective in forming aphotoresist film having a low rate of dissolution in an alkalinedeveloper and capable of maintaining the height of a fine pattern formedtherein.

The resist composition of the invention is advantageously used as achemically amplified positive resist composition. In addition to theadditive polymer described above, the chemically amplified positiveresist composition generally comprises a base resin comprising at leastrecurring units having acid labile groups and recurring units havinghydroxy groups and/or adhesive groups of lactone ring.

Since the base resin includes recurring units having hydroxy groupsand/or adhesive groups of lactone ring, the chemically amplifiedpositive resist composition ensures tight adhesion to a substrate. Sincethe base resin includes recurring units having acid labile groups, theacid labile groups are deprotected with the acid generated by the acidgenerator during exposure so that the exposed area of resist isconverted to be soluble in a developer, ensuring that a pattern isformed at a very high precision.

Base Resin

Suitable base resins include, but are not limited to, those polymerscomprising units of the following formula (R1) and/or (R2) and having aweight average molecular weight (Mw) of about 1,000 to about 100,000,especially about 3,000 to about 30,000, as measured by GPC versuspolystyrene standards.

Herein, R⁰⁰¹ is hydrogen, methyl or —CH₂CO₂R⁰⁰³.

R⁰⁰² is hydrogen, methyl or —CO₂R⁰⁰³.

R⁰⁰³ is a straight, branched or cyclic C₁-C₁₅ alkyl group, for example,methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl, ethylcyclopentyl,butylcyclopentyl, ethylcyclohexyl, butylcyclohexyl, adamantyl,ethyladamantyl, and butyladamantyl.

R⁰⁰⁴ is hydrogen or a monovalent C₁-C₁₅ hydrocarbon group having atleast one of fluorinated substituent groups, carboxyl groups andhydroxyl groups, for example, hydrogen, carboxyethyl, carboxybutyl,carboxycyclopentyl, carboxycyclohexyl, carboxynorbornyl,carboxyadamantyl, hydroxyethyl, hydroxybutyl, hydroxycyclopentyl,hydroxycyclohexyl, hydroxynorbornyl, hydroxyadamantyl,hydroxyhexafluoroisopropylcyclohexyl, anddi(hydroxyhexafluoroisopropyl)cyclohexyl.

At least one of R⁰⁰⁵ to R⁰⁰⁸ represents a monovalent C₁-C₁₅ hydrocarbongroup having at least one of fluorinated substituent groups, carboxylgroups and hydroxyl groups while the remaining R's independentlyrepresent hydrogen or straight, branched or cyclic C₁-C₁₅ alkyl groups.Examples of the monovalent C₁-C₁₅ hydrocarbon group having at least oneof fluorinated substituent groups, carboxyl groups and hydroxyl groupsinclude carboxy, carboxymethyl, carboxyethyl, carboxybutyl,hydroxymethyl, hydroxyethyl, hydroxybutyl, 2-carboxyethoxycarbonyl,4-carboxybutoxycarbonyl, 2-hydroxyethoxycarbonyl,4-hydroxybutoxycarbonyl, carboxycyclopentyloxycarbonyl,carboxycyclohexyloxycarbonyl, carboxynorbornyloxycarbonyl,carboxyadamantyloxycarbonyl, hydroxycyclopentyloxycarbonyl,hydroxycyclohexyloxycarbonyl, hydroxynorbornyloxycarbonyl,hydroxyadamantyloxycarbonyl,hydroxyhexafluoroisopropylcyclohexyloxycarbonyl, anddi(hydroxyhexafluoroisopropyl)cyclohexyloxycarbonyl. Examples of thestraight, branched or cyclic C₁-C₁₅ alkyl group are the same asexemplified for R⁰⁰³.

Alternatively, two of R⁰⁰⁵ to R⁰⁰⁸ (e.g., a pair of R⁰⁰⁵ and R⁰⁰⁶, R⁰⁰⁶and R⁰⁰⁷) may bond together to form a ring with the carbon atom(s) towhich they are attached. In that event, at least one of R⁰⁰⁵ to R⁰⁰⁸ isa divalent C₁-C₁₅ hydrocarbon group having at least one of fluorinatedsubstituent groups, carboxyl groups and hydroxyl groups, while theremaining are independently a single bond or a straight, branched orcyclic C₁-C₁₅ alkylene group. Examples of the divalent C₁-C₁₅hydrocarbon group having at least one of fluorinated substituent groups,carboxyl groups and hydroxyl groups include the groups exemplified asthe monovalent hydrocarbon group having at least one of fluorinatedsubstituent groups, carboxyl groups and hydroxyl groups, with onehydrogen atom eliminated therefrom. Examples of the straight, branchedor cyclic C₁-C₁₅ alkyl groups include the groups exemplified for R⁰⁰³,with one hydrogen atom eliminated therefrom.

R⁰⁰⁹ is a monovalent C₃-C₁₅ hydrocarbon group containing a —CO₂— partialstructure, for example, 2-oxooxolan-3-yl, 4,4-dimethyl-2-oxooxolan-3-yl,4-methyl-2-oxooxan-4-yl, 2-oxo-1,3-dioxolan-4-ylmethyl, and5-methyl-2-oxooxolan-5-yl.

At least one of R⁰¹⁰ to R⁰¹³ is a monovalent C₂-C₁₅ hydrocarbon groupcontaining a —CO₂— partial structure, while the remaining R's areindependently hydrogen or straight, branched or cyclic C₁-C₁₅ alkylgroups. Examples of the monovalent C₂-C₁₅ hydrocarbon group containing a—CO₂— partial structure include 2-oxooxolan-3-yloxycarbonyl,4,4-dimethyl-2-oxooxolan-3-yloxycarbonyl,4-methyl-2-oxooxan-4-yloxycarbonyl,2-oxo-1,3-dioxolan-4-ylmethyloxycarbonyl, and5-methyl-2-oxooxolan-5-yloxycarbonyl. Examples of the straight, branchedor cyclic C₁-C₁₅ alkyl groups are the same as exemplified for R⁰⁰³.

Alternatively, two of R⁰¹⁰ to R⁰¹³ (e.g., a pair of R⁰¹⁰ and R⁰¹⁰, R⁰¹¹and R⁰¹²) may bond together to form a ring with the carbon atom(s) towhich they are attached. In that event, at least one of R⁰¹⁰ to R⁰¹³ isa divalent C₂-C₁₅ hydrocarbon group containing a —CO₂— partialstructure, while the remaining are independently a single bond or astraight, branched or cyclic C₁-C₁₅ alkylene group. Examples of thedivalent C₂-C₁₅ hydrocarbon group containing a —CO₂— partial structureinclude 1-oxo-2-oxapropane-1,3-diyl, 1,3-dioxo-2-oxapropane-1,3-diyl,1-oxo-2-oxabutane-1,4-diyl, and 1,3-dioxo-2-oxabutane-1,4-diyl, as wellas the groups exemplified as the monovalent hydrocarbon group containinga —CO₂— partial structure, with one hydrogen atom eliminated therefrom.Examples of the straight, branched or cyclic C₁-C₁₅ alkylene groupsinclude the groups exemplified for R⁰⁰³, with one hydrogen atomeliminated therefrom.

R⁰¹⁴ is a polycyclic C₇-C₁₅ hydrocarbon group or an alkyl groupcontaining a polycyclic hydrocarbon group, for example, norbornyl,bicyclo[3.3.1]nonyl, tricyclo[5.2.1.0^(2,6)]decyl, adamantyl,ethyladamantyl, butyladamantyl, norbornylmethyl, and adamantylmethyl.

R⁰¹⁵ is an acid labile group, which will be described later.

X is —CH₂ or an oxygen atom.

The subscript k is 0 or 1.

The acid labile groups represented by R⁰¹⁵ may be selected from avariety of such groups. Examples of the acid labile group are groups ofthe following general formulae (L1) to (L4), tertiary alkyl groups of 4to 20 carbon atoms, preferably 4 to 15 carbon atoms, trialkylsilylgroups in which each alkyl moiety has 1 to 6 carbon atoms, and oxoalkylgroups of 4 to 20 carbon atoms.

The broken line indicates a valence bond.

In formula (L1), R^(L01) and R^(L02) are hydrogen or straight, branchedor cyclic alkyl groups of 1 to 18 carbon atoms, preferably 1 to 10carbon atoms. Examples include hydrogen, methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, cyclopentyl, cyclohexyl,2-ethylhexyl, n-octyl, and adamantyl. R^(L03) is a monovalenthydrocarbon group of 1 to 18 carbon atoms, preferably 1 to 10 carbonatoms, which may contain a hetero atom such as oxygen, examples of whichinclude unsubstituted straight, branched or cyclic alkyl groups andstraight, branched or cyclic alkyl groups in which some hydrogen atomsare replaced by hydroxyl, alkoxy, oxo, amino, alkylamino or the like.Examples of the straight, branched or cyclic alkyl groups are asexemplified above for R^(L01) and R^(L02), and examples of thesubstituted alkyl groups are shown below.

A pair of R^(L01) and R^(L02), R^(L01) and R^(L03), or R^(L02) andR^(L03) may bond together to form a ring with the carbon and oxygenatoms to which they are attached. Each of R^(L01), R^(L02) and R^(L03)is a straight or branched alkylene group of 1 to 18 carbon atoms,preferably 1 to 10 carbon atoms when they form a ring.

In formula (L2), R^(L04) is a tertiary alkyl group of 4 to 20 carbonatoms, preferably 4 to 15 carbon atoms, a trialkylsilyl group in whicheach alkyl moiety has 1 to 6 carbon atoms, an oxoalkyl group of 4 to 20carbon atoms, or a group of formula (L1). Exemplary tertiary alkylgroups are tert-butyl, tert-amyl, 1,1-diethylpropyl,2-cyclopentylpropan-2-yl, 2-cyclohexylpropan-2-yl,2-(bicyclo[2.2.1]heptan-2-yl)propan-2-yl, 2-(adamantan-1-yl)propan-2-yl,1-ethylcyclopentyl, 1-butylcyclopentyl, 1-ethylcyclohexyl,1-butylcyclohexyl, 1-ethyl-2-cyclopentenyl, 1-ethyl-2-cyclohexenyl,2-methyl-2-adamantyl, and 2-ethyl-2-adamantyl. Exemplary trialkylsilylgroups are trimethylsilyl, triethylsilyl, and dimethyl-tert-butylsilyl.Exemplary oxoalkyl groups are 3-oxocyclohexyl, 4-methyl-2-oxooxan-4-yl,and 5-methyl-2-oxooxolan-5-yl. In formula (L2), y is an integer of 0 to6.

In formula (L3), R^(L05) is a substituted or unsubstituted, C₁-C₁₀straight, branched or cyclic alkyl group or a substituted orunsubstituted C₆-C₂₀ aryl group. Examples of the substituted orunsubstituted alkyl groups include straight, branched or cyclic onessuch as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, cyclohexyl andbicyclo[2.2.1]heptyl; substituted forms of the foregoing in which somehydrogen atoms are replaced by hydroxyl, alkoxy, carboxy,alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto, alkylthio,sulfo or other groups; and substituted forms of the foregoing in whichsome of the methylene groups are replaced by oxygen or sulfur atoms.Exemplary substituted or unsubstituted aryl groups are phenyl,methylphenyl, naphthyl, anthryl, phenanthryl, and pyrenyl. In formula(L3), m is 0 or 1, n is 0, 1, 2 or 3, and 2m+n is equal to 2 or 3.

In formula (L4), R^(L06) is a substituted or unsubstituted, C₁-C₁₀straight, branched or cyclic alkyl group or a substituted orunsubstituted C₆-C₂₀ aryl group. Examples of these groups are the sameas exemplified for R^(L05). R^(L07) to R^(L16) independently representhydrogen or monovalent C₁-C₁₅ hydrocarbon groups. Exemplary hydrocarbongroups are straight, branched or cyclic alkyl groups such as methyl,ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, tert-amyl,n-pentyl, n-hexyl, n-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl,cyclopentylmethyl, cyclopentylethyl, cyclopentylbutyl, cyclohexylmethyl,cyclohexylethyl and cyclohexylbutyl, and substituted forms of theforegoing in which some hydrogen atoms are replaced by hydroxyl, alkoxy,carboxy, alkoxycarbonyl, oxo, amino, alkylamino, cyano, mercapto,alkylthio, sulfo or other groups. Alternatively, two of R^(L07) toR^(L16) may bond together to form a ring with the carbon atom to whichthey are attached (for example, a pair of R^(L07) and R^(L08), R^(L07)and R^(L09), R^(L08) and R^(L10), R^(L09) and R^(L10), R^(L11) andR^(L12), R^(L13) and R^(L14), or a similar pair form a ring). Each ofR^(L07) to R^(L16) represents a divalent C₁-C₁₅ hydrocarbon group whenthey form a ring, examples of which are the ones exemplified above forthe monovalent hydrocarbon groups, with one hydrogen atom beingeliminated. Two of R^(L07) to R^(L16) which are attached to vicinalcarbon atoms (for example, a pair of R^(L07) and R^(L09), R^(L09) andR^(L15), R^(L13) and R^(L15), or a similar pair) may bond togetherdirectly to form a double bond.

Of the acid labile groups of formula (L1), the straight and branchedones are exemplified by the following groups.

Of the acid labile groups of formula (L1), the cyclic ones are, forexample, tetrahydrofuran-2-yl, 2-methyltetrahydrofuran-2-yl,tetrahydropyran-2-yl, and 2-methyltetrahydropyran-2-yl.

Examples of the acid labile groups of formula (L2) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1,1-diethylpropyloxycarbonyl,1,1-diethylpropyloxycarbonylmethyl, 1-ethylcyclopentyloxycarbonyl,1-ethylcyclopentyloxycarbonylmethyl, 1-ethyl-2-cyclopentenyloxycarbonyl,1-ethyl-2-cyclopentenyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl, and2-tetrahydrofuranyloxycarbonylmethyl groups.

Examples of the acid labile groups of formula (L3) include1-methylcyclopentyl, 1-ethylcyclopentyl, 1-n-propylcyclopentyl,1-isopropylcyclopentyl, 1-n-butylcyclopentyl, 1-sec-butylcyclopentyl,1-cyclohexylcyclopentyl, 1-(4-methoxy-n-butyl)cyclopentyl,1-(bicyclo[2.2.1]heptan-2-yl)cyclopentyl,1-(7-oxabicyclo[2.2.1]heptan-2-yl)cyclopentyl, 1-methylcyclohexyl,1-ethylcyclohexyl, 3-methyl-1-cyclopenten-3-yl,3-ethyl-1-cyclopenten-3-yl, 3-methyl-1-cyclohexen-3-yl, and3-ethyl-1-cyclohexen-3-yl groups.

The acid labile groups of formula (L4) are preferably groups of thefollowing formulae (L4-1) to (L4-4).

In formulae (L4-1) to (L4-4), the broken line indicates a bonding siteand direction. R^(L41) is each independently selected from monovalenthydrocarbon groups, typically straight, branched or cyclic C₁-C₁₀ alkylgroups, for example, methyl, ethyl, propyl, isopropyl, n-butyl,sec-butyl, tert-butyl, tert-amyl, n-pentyl, n-hexyl, cyclopentyl, andcyclohexyl.

For formulas (L4-1) to (L4-4), there can exist enantiomers anddiastereomers. Each of formulae (L4-1) to (L4-4) collectively representsall such stereoisomers. Such stereoisomers may be used alone or inadmixture.

For example, the general formula (L4-3) represents one or a mixture oftwo selected from groups having the following general formulas (L4-3-1)and (L4-3-2).

Herein R^(L41) is as defined above.

Similarly, the general formula (L4-4) represents one or a mixture of twoor more selected from groups having the following general formulas(L4-4-1) to (L4-4-4).

Herein R^(L41) is as defined above.

Each of formulas (L4-1) to (L4-4), (L4-3-1) and (L4-3-2), and (L4-4-1)to (L4-4-4) collectively represents an enantiomer thereof and a mixtureof enantiomers.

It is noted that in the above formulas (L4-1) to (L4-4), (L4-3-1) and(L4-3-2), and (L4-4-1) to (L4-4-4), the bond direction is on the exoside relative to the bicyclo[2.2.1]heptane ring, which ensures highreactivity for acid catalyzed elimination reaction (see JP-A2000-336121). In preparing these monomers having a tertiary exo-alkylgroup of bicyclo[2.2.1]heptane skeleton as a substituent group, theremay be contained monomers substituted with an endo-alkyl group asrepresented by the following formulas (L4-1-endo) to (L4-4-endo). Forgood reactivity, an exo proportion of at least 50 mol % is preferred,with an exo proportion of at least 80 mol % being more preferred.

Herein R^(L41) is as defined above.

Illustrative examples of the acid labile group of formula (L4) are givenbelow.

Examples of the tertiary C₄-C₂₀ alkyl, tri(C₁-C₆-alkyl)silyl and C₄-C₂₀oxoalkyl groups included in the acid labile groups represented by R⁰¹⁵are as exemplified above for R^(L04).

In formula (R²), R⁰¹⁶ is hydrogen or methyl. R⁰¹⁷ is a straight,branched or cyclic C₁-C₈ alkyl group.

In formula (R1), the subscripts a1′, a2′, a3′, b1′, b2′, b3′, c1, c2′,c3′, d1′, d2′, d3′, and e′ are numbers from 0 to less than 1, satisfyinga1′+a2′+a3′+b1′+b2′+b3′+c1′+c2′+c3′+d1′+d2′+d3′+e′=1. In formula (R2),f′, g′, h′, i′, j′, k′, l′, and m′ are numbers from 0 to less than 1,satisfying f′+g′+h′+i′+j′+k′+l′+m′=1; x′, y′ and z′ are each an integerof 0 to 3, satisfying 1≦x′+y′+z′≦5 and 1≦y′+z′≦3. In addition, one ormore monomers selected from indenes, norbornadienes, acenaphthylenes andvinyl ethers may be copolymerized.

When the resist composition of the invention is a negative one, the baseresin is selected from polymers of formulae (R1) and (R2) wherein d1′,d2′, d3′, g′, and m′ are zero.

Examples of the recurring units incorporated at compositional ratio a1′in formula (R1) are shown below, though not limited thereto.

Examples of the recurring units incorporated at compositional ratio b1′in formula (R1) are shown below, though not limited thereto.

Examples of the recurring units incorporated at compositional ratio d1′in formula (R1) are shown below, though not limited thereto.

Examples of polymers comprising recurring units in compositional ratiosa3′, b3′, c3′ and d3′ in formula (R1) are shown below, though notlimited thereto.

The polymer used as the base resin is not limited to one type and amixture of two or more polymers may be added. The use of plural polymersallows for easy adjustment of resist properties.

Acid Generator

In the resist composition of the invention, an acid generator,specifically a compound capable of generating an acid in response toactinic light or radiation may be included in order that the resistcomposition function as a chemically amplified positive resistcomposition. The acid generator may be any compound capable ofgenerating an acid upon exposure of high-energy radiation, which isgenerally referred to as “photoacid generator” or PAG. Suitablephotoacid generators include sulfonium salts, iodonium salts,sulfonyldiazomethane, N-sulfonyloxyimide, and oxime-O-sulfonate acidgenerators. Exemplary acid generators are given below while they may beused alone or in admixture of two or more.

Sulfonium salts are salts of sulfonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary sulfonium cations includetriphenylsulfonium, (4-tert-butoxyphenyl)diphenylsulfonium,bis(4-tert-butoxyphenyl)phenylsulfonium,tris(4-tert-butoxyphenyl)sulfonium,(3-tert-butoxyphenyl)diphenylsulfonium,bis(3-tert-butoxyphenyl)phenylsulfonium,tris(3-tert-butoxyphenyl)sulfonium,(3,4-di-tert-butoxyphenyl)diphenylsulfonium,bis(3,4-di-tert-butoxyphenyl)phenylsulfonium,tris(3,4-di-tert-butoxyphenyl)sulfonium,diphenyl(4-thiophenoxyphenyl)sulfonium,(4-tert-butoxycarbonylmethyloxyphenyl)diphenylsulfonium,tris(4-tert-butoxycarbonylmethyloxyphenyl)sulfonium,(4-tert-butoxyphenyl)bis(4-dimethylaminophenyl)sulfonium,tris(4-dimethylaminophenyl)sulfonium, 2-naphthyldiphenylsulfonium,dimethyl-2-naphthylsulfonium, 4-hydroxyphenyldimethylsulfonium,4-methoxyphenyldimethylsulfonium, trimethylsulfonium,2-oxocyclohexylcyclohexylmethylsulfonium, trinaphthylsulfonium,tribenzylsulfonium, diphenylmethylsulfonium, dimethylphenylsulfonium,2-oxo-2-phenylethylthiacyclopentanium,4-n-butoxynaphthyl-1-thiacyclopentanium, and2-n-butoxynaphthyl-1-thiacyclopentanium. Exemplary sulfonates includetrifluoromethanesulfonate, pentafluoroethanesulfonate,nonafluorobutanesulfonate, dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4′-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Sulfonium salts based on combinationof the foregoing examples are included.

Iodonium salts are salts of iodonium cations with sulfonates,bis(substituted alkylsulfonyl)imides and tris(substitutedalkylsulfonyl)methides. Exemplary iodonium cations are aryliodoniumcations including diphenyliodinium, bis(4-tert-butylphenyl)iodonium,4-tert-butoxyphenylphenyliodonium, and 4-methoxyphenylphenyliodonium.Exemplary sulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,4-(4-toluenesulfonyloxy)benzenesulfonate, naphthalenesulfonate,camphorsulfonate, octanesulfonate, dodecylbenzenesulfonate,butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-ylethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Exemplary bis(substituted alkylsulfonyl)imides includebistrifluoromethylsulfonylimide, bispentafluoroethylsulfonylimide,bisheptafluoropropylsulfonylimide, and 1,3-propylenebissulfonylimide. Atypical tris(substituted alkylsulfonyl)methide istristrifluoromethylsulfonylmethide. Iodonium salts based on combinationof the foregoing examples are included.

Exemplary sulfonyldiazomethane compounds include bissulfonyldiazomethanecompounds and sulfonyl-carbonyldiazomethane compounds such asbis(ethylsulfonyl)diazomethane, bis(1-methylpropylsulfonyl)diazomethane,bis(2-methylpropylsulfonyl)diazomethane,bis(1,1-dimethylethylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(perfluoroisopropylsulfonyl)diazomethane,bis(phenylsulfonyl)diazomethane,bis(4-methylphenylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(2-naphthylsulfonyl)diazomethane,bis(4-acetyloxyphenylsulfonyl)diazomethane,bis(4-methanesulfonyloxyphenylsulfonyl)diazomethane,bis(4-(4-toluenesulfonyloxy)phenylsulfonyl)diazomethane,bis(4-(n-hexyloxyphenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,4-methylphenylsulfonylbenzoyldiazomethane,tert-butylcarbonyl-4-methylphenylsulfonyldiazomethane,2-naphthylsulfonylbenzoyldiazomethane,4-methylphenylsulfonyl-2-naphthoyldiazomethane,methylsulfonylbenzoyldiazomethane, andtert-butoxycarbonyl-4-methylphenylsulfonyldiazomethane.

N-sulfonyloxyimide photoacid generators include combinations of imideskeletons with sulfonates. Exemplary imide skeletons are succinimide,naphthalene dicarboxylic acid imide, phthalimide, cyclohexyldicarboxylicacid imide, 5-norbornene-2,3-dicarboxylic acid imide, and7-oxabicyclo[2.2.1]-5-heptene-2,3-dicarboxylic acid imide. Exemplarysulfonates include trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, mesitylenesulfonate,2,4,6-triisopropylbenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Benzoinsulfonate photoacid generators include benzoin tosylate, benzoinmesylate, and benzoin butanesulfonate.

Pyrogallol trisulfonate photoacid generators include pyrogallol,phloroglucinol, catechol, resorcinol, and hydroquinone, in which all thehydroxyl groups are substituted by trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxypropanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.

Nitrobenzyl sulfonate photoacid generators include 2,4-dinitrobenzylsulfonate, 2-nitrobenzyl sulfonate, and 2,6-dinitrobenzyl sulfonate,with exemplary sulfonates including trifluoromethanesulfonate,pentafluoroethanesulfonate, nonafluorobutanesulfonate,dodecafluorohexanesulfonate,pentafluoroethylperfluorocyclohexanesulfonate,heptadecafluorooctanesulfonate, 2,2,2-trifluoroethanesulfonate,pentafluorobenzenesulfonate, 4-trifluoromethylbenzenesulfonate,4-fluorobenzenesulfonate, toluenesulfonate, benzenesulfonate,naphthalenesulfonate, camphorsulfonate, octanesulfonate,dodecylbenzenesulfonate, butanesulfonate, methanesulfonate,2-benzoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-(4-phenylbenzoyloxy)propanesulfonate,1,1,3,3,3-pentafluoro-2-pivaloyloxypropanesulfonate,2-cyclohexanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-furoyloxypropanesulfonate,2-naphthoyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-(4-tert-butylbenzoyloxy)-1,1,3,3,3-pentafluoropropanesulfonate,2-adamantanecarbonyloxy-1,1,3,3,3-pentafluoropropanesulfonate,2-acetyloxy-1,1,3,3,3-pentafluoropropanesulfonate,1,1,3,3,3-pentafluoro-2-hydroxypropanesulfonate,1,1,3,3,3-pentafluoro-2-tosyloxypropanesulfonate,1,1-difluoro-2-naphthyl-ethanesulfonate,1,1,2,2-tetrafluoro-2-(norbornan-2-yl)ethanesulfonate, and1,1,2,2-tetrafluoro-2-(tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodec-3-en-8-yl)ethanesulfonate.Also useful are analogous nitrobenzyl sulfonate compounds in which thenitro group on the benzyl side is substituted by a trifluoromethylgroup.

Sulfone photoacid generators include bis(phenylsulfonyl)methane,bis(4-methylphenylsulfonyl)methane, bis(2-naphthylsulfonyl)methane,2,2-bis(phenylsulfonyl)propane, 2,2-bis(4-methylphenylsulfonyl)propane,2,2-bis(2-naphthylsulfonyl)propane,2-methyl-2-(p-toluenesulfonyl)propiophenone,2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane, and2,4-dimethyl-2-(p-toluenesulfonyl)pentan-3-one.

Photoacid generators in the form of glyoxime derivatives are describedin Japanese Patent No. 2,906,999 and JP-A 9-301948 and includebis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,bis-O-(methanesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-α-dimethylglyoxime,bis-O-(10-camphorsulfonyl)-α-dimethylglyoxime,bis-O-(benzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-α-dimethylglyoxime,bis-O-(xylenesulfonyl)-α-dimethylglyoxime,bis-O-(trifluoromethanesulfonyl)-nioxime,bis-O-(2,2,2-trifluoroethanesulfonyl)-nioxime,bis-O-(10-camphorsulfonyl)-nioxime, bis-O-(benzenesulfonyl)-nioxime,bis-O-(p-fluorobenzenesulfonyl)-nioxime,bis-O-(p-trifluoromethylbenzenesulfonyl)-nioxime, andbis-O-(xylenesulfonyl)-nioxime.

Also included are the oxime sulfonates described in U.S. Pat. No.6,004,724, for example,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)phenylacetonitrile,(5-(4-toluenesulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-(10-camphorsulfonyl)oxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,(5-n-octanesulfonyloxyimino-5H-thiophen-2-ylidene)(2-methylphenyl)acetonitrile,etc. Also included are the oxime sulfonates described in U.S. Pat. No.6,916,591, for example,(5-(4-(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrileand(5-(2,5-bis(4-toluenesulfonyloxy)benzenesulfonyl)oxyimino-5H-thiophen-2-ylidene)phenylacetonitrile.

Also included are the oxime sulfonates described in U.S. Pat. No.6,261,738 and JP-A 2000-314956, for example,2,2,2-trifluoro-1-phenyl-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(4-methoxyphenylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanone oxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-phenyl-ethanoneoxime-O-(2,4,6-trimethylphenylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-(methylsulfonate);2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphorylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthylsulfonate);2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthylsulfonate);2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylthiophenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,3,3,4,4,4-heptafluoro-1-phenyl-butanoneoxime-O-(10-camphorylsulfonate); 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-10-camphorylsulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(1-naphthyl)-sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate; 2,2,2-trifluoro-1-(phenyl)-ethanoneoxime-O-(2,4,6-trimethylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(4-methylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4-dimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(10-camphoryl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(1-naphthyl)sulfonate;2,2,2-trifluoro-1-(2,4,6-trimethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(3,4-dimethoxyphenyl)-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methylphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanoneoxime-O-(4-dodecylphenyl)-sulfonate;2,2,2-trifluoro-1-(4-methoxyphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(4-methoxyphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(4-dodecylphenyl)sulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanone oxime-O-octylsulfonate;2,2,2-trifluoro-1-(4-thiomethylphenyl)-ethanoneoxime-O-(2-naphthyl)sulfonate;2,2,2-trifluoro-1-(2-methylphenyl)-ethanone oxime-O-methylsulfonate;2,2,2-trifluoro-1-(4-methylphenyl)ethanone oxime-O-phenylsulfonate;2,2,2-trifluoro-1-(4-chlorophenyl)-ethanone oxime-O-phenylsulfonate;2,2,3,3,4,4,4-heptafluoro-1-(phenyl)-butanoneoxime-O-(10-camphoryl)sulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-methylsulfonate;2,2,2-trifluoro-1-[4-(phenyl-1,4-dioxa-but-1-yl)phenyl]-ethanoneoxime-O-methylsulfonate; 2,2,2-trifluoro-1-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-2-naphthyl-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzylphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylsulfonylphenyl]-ethanoneoxime-O-propylsulfonate;1,3-bis[1-(4-phenoxyphenyl)-2,2,2-trifluoroethanoneoxime-O-sulfonyl]phenyl;2,2,2-trifluoro-1-[4-methylsulfonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methylcarbonyloxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[6H,7H-5,8-dioxonaphth-2-yl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-methoxycarbonylmethoxyphenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[4-(methoxycarbonyl)-(4-amino-1-oxa-pent-1-yl)-phenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[3,5-dimethyl-4-ethoxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[4-benzyloxyphenyl]-ethanoneoxime-O-propylsulfonate; 2,2,2-trifluoro-1-[2-thiophenyl]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-[1-dioxa-thiophen-2-yl)]-ethanoneoxime-O-propylsulfonate;2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(trifluoromethanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(trifluoromethanesulfonate);2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-propanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(1-propanesulfonate); and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(1-butanesulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)-ethanoneoxime(1-butanesulfonate). Also included are the oxime sulfonatesdescribed in U.S. Pat. No. 6,916,591, for example,2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(4-(4-methylphenylsulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(4-(4-methylphenylsulfonyloxy)phenylsulfonate) and2,2,2-trifluoro-1-(4-(3-(4-(2,2,2-trifluoro-1-(2,5-bis(4-methylphenylsulfonyloxy)-benzenesulfonyloxy)phenylsulfonyloxyimino)-ethyl)-phenoxy)-propoxy)-phenyl)ethanoneoxime(2,5-bis(4-methylphenylsulfonyloxy)benzenesulfonyloxy)phenylsulfonate).

Also included are the oxime sulfonates described in JP-A 9-95479 andJP-A 9-230588 and the references cited therein, for example,α-(p-toluenesulfonyloxyimino)-phenylacetonitrile,α-(p-chlorobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitrobenzenesulfonyloxyimino)-phenylacetonitrile,α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-phenylacetonitrile,α-(benzenesulfonyloxyimino)-4-chlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,4-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-2,6-dichlorophenylacetonitrile,α-(benzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,α-(2-chlorobenzenesulfonyloxyimino)-4-methoxyphenylacetonitrile,α-(benzenesulfonyloxyimino)-2-thienylacetonitrile,α-(4-dodecylbenzenesulfonyloxyimino)-phenylacetonitrile,α-[(4-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile,α-(tosyloxyimino)-3-thienylacetonitrile,α-(methylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(n-butylsulfonyloxyimino)-1-cyclopentenylacetonitrile,α-(ethylsulfonyloxyimino)-1-cyclohexenylacetonitrile,α-(isopropylsulfonyloxyimino)-1-cyclohexenylacetonitrile, andα-(n-butylsulfonyloxyimino)-1-cyclohexenylacetonitrile.

Also included are oxime sulfonates having the formula:

wherein R^(s1) is a substituted or unsubstituted haloalkylsulfonyl orhalobenzenesulfonyl group of 1 to 10 carbon atoms, R^(s2) is a haloalkylgroup of 1 to 11 carbon atoms, and Ar^(s1) is substituted orunsubstituted aromatic or hetero-aromatic group, as described in WO2004/074242. Examples include2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene,2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-4-biphenyl,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-4-biphenyl,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-4-biphenyl.

Suitable bisoxime sulfonates include those described in JP-A 9-208554,for example,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-p-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(benzenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(methanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(butanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(10-camphorsulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(4-toluenesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(trifluoromethanesulfonyloxy)imino)-m-phenylenediacetonitrile,bis(α-(4-methoxybenzenesulfonyloxy)imino)-m-phenylenediacetonitrile,etc.

Of these, preferred photoacid generators are sulfonium salts,bissulfonyldiazomethanes, N-sulfonyloxyimides, oxime-O-sulfonates andglyoxime derivatives. More preferred photoacid generators are sulfoniumsalts, bissulfonyldiazomethanes, N-sulfonyloxyimides, andoxime-O-sulfonates. Typical examples include triphenylsulfoniump-toluenesulfonate, triphenylsulfonium camphorsulfonate,triphenylsulfonium pentafluorobenzenesulfonate, triphenylsulfoniumnonafluorobutanesulfonate, triphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, triphenylsulfonium2,4,6-triisopropylbenzenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniump-toluenesulfonate, 4-tert-butoxyphenyldiphenylsulfoniumcamphorsulfonate, 4-tert-butoxyphenyldiphenylsulfonium4-(4′-toluenesulfonyloxy)benzenesulfonate, tris(4-methylphenyl)sulfoniumcamphorsulfonate, tris(4-tert-butylphenyl)sulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium camphorsulfonate,4-tert-butylphenyldiphenylsulfonium nonafluoro-1-butanesulfonate,4-tert-butylphenyldiphenylsulfoniumpentafluoroethylperfluorocyclohexanesulfonate,4-tert-butylphenyldiphenylsulfonium perfluoro-1-octanesulfonate,triphenylsulfonium 1,1-difluoro-2-naphthyl-ethanesulfonate,triphenylsulfonium1,1,2,2-tetrafluoro-2-(norbornan-2-yl)-ethanesulfonate,bis(tert-butylsulfonyl)diazomethane,bis(cyclohexylsulfonyl)diazomethane,bis(2,4-dimethylphenylsulfonyl)diazomethane,bis(4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(3,5-dimethyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(2-methyl-5-isopropyl-4-(n-hexyloxy)phenylsulfonyl)diazomethane,bis(4-tert-butylphenylsulfonyl)diazomethane,N-camphorsulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,N-p-toluenesulfonyloxy-5-norbornene-2,3-dicarboxylic acid imide,2-[2,2,3,3,4,4,5,5-octafluoro-1-(nonafluorobutylsulfonyloxyimino)-pentyl]-fluorene,2-[2,2,3,3,4,4-pentafluoro-1-(nonafluorobutylsulfonyloxyimino)-butyl]-fluorene,and2-[2,2,3,3,4,4,5,5,6,6-decafluoro-1-(nonafluorobutylsulfonyloxyimino)-hexyl]-fluorene.

In the chemically amplified resist composition, an appropriate amount ofthe photoacid generator is, but not limited to, 0.1 to 20 parts, andespecially 0.1 to 10 parts by weight per 100 parts by weight of the baseresin. If the amount of the PAG is up to 20 phr, the resultingphotoresist film has a sufficiently high transmittance to minimize arisk of degrading resolution. The PAG may be used alone or in admixtureof two or more. The transmittance of the resist film can be controlledby using a PAG having a low transmittance at the exposure wavelength andadjusting the amount of the PAG added.

In the resist composition, there may be added a compound which isdecomposed with an acid to generate another acid, that is,acid-amplifier compound. For these compounds, reference should be madeto J. Photopolym. Sci. and Tech., 8, 43-44, 45-46 (1995), and ibid., 9,29-30 (1996).

Examples of the acid-amplifier compound includetert-butyl-2-methyl-2-tosyloxymethyl acetoacetate and2-phenyl-2-(2-tosyloxyethyl)-1,3-dioxolane, but are not limited thereto.Of well-known photoacid generators, many of those compounds having poorstability, especially poor thermal stability exhibit an acidamplifier-like behavior.

In the resist composition, an appropriate amount of the acid-amplifiercompound is up to 2 parts, and preferably up to 1 part by weight per 100parts by weight of the base resin. Up to 2 phr of the acid-amplifiercompound allows for diffusion control, minimizing a risk of degradingresolution and pattern profile.

In addition to the base resin and PAG as well as the additive polymer,the resist composition of the invention may further comprise at leastone of an organic solvent, a basic compound, a dissolution regulator,and a surfactant.

Solvent

The organic solvent used herein may be any organic solvent in which thebase resin, acid generator, and other components are soluble.Illustrative, non-limiting, examples of the organic solvent includeketones such as cyclohexanone and methyl-2-n-amyl ketone; alcohols suchas 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol,and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethylether, ethylene glycol monomethyl ether, propylene glycol monoethylether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether,and diethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate (PGMEA), propylene glycol monoethyl etheracetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone. These solvents may beused alone or in combinations of two or more thereof. Of the aboveorganic solvents, it is recommended to use diethylene glycol dimethylether, 1-ethoxy-2-propanol, propylene glycol monomethyl ether acetate,and mixtures thereof because the acid generator is most soluble therein.

An appropriate amount of the organic solvent used is about 200 to 3,000parts, especially about 400 to 2,500 parts by weight per 100 parts byweight of the base resin.

Basic Compound

In the resist composition, an organic nitrogen-containing compound orcompounds may be compounded as the basic compound. The organicnitrogen-containing compound used herein is preferably a compoundcapable of suppressing the rate of diffusion when the acid generated bythe acid generator diffuses within the resist film. The inclusion oforganic nitrogen-containing compound holds down the rate of aciddiffusion within the resist film, resulting in better resolution. Inaddition, it suppresses changes in sensitivity following exposure andreduces substrate and environment dependence, as well as improving theexposure latitude and the pattern profile.

Suitable organic nitrogen-containing compounds include primary,secondary, and tertiary aliphatic amines, mixed amines, aromatic amines,heterocyclic amines, nitrogen-containing compounds having carboxylgroup, nitrogen-containing compounds having sulfonyl group,nitrogen-containing compounds having hydroxyl group, nitrogen-containingcompounds having hydroxyphenyl group, alcoholic nitrogen-containingcompounds, amide derivatives, imide derivatives, and carbamatederivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,isobutylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine, diisopropylamine,di-n-butylamine, diusobutylamine, di-sec-butylamine, dipentylamine,dicyclopentylamine, dihexylamine, dicyclohexylamine, diheptylamine,dioctylamine, dinonylamine, didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, triisopropylamine, tri-n-butylamine,triisobutylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic and heterocyclicamines include aniline derivatives (e.g., aniline, N-methylaniline,N-ethylaniline, N-propylaniline, N,N-dimethylaniline, 2-methylaniline,3-methylaniline, 4-methylaniline, ethylaniline, propylaniline,trimethylaniline, 2-nitroaniline, 3-nitroaniline, 4-nitroaniline,2,4-dinitroaniline, 2,6-dinitroaniline, 3,5-dinitroaniline, andN,N-dimethyltoluidine), diphenyl(p-tolyl)amine, methyldiphenylamine,triphenylamine, phenylenediamine, naphthylamine, diaminonaphthalene,pyrrole derivatives (e.g., pyrrole, 2H-pyrrole, 1-methylpyrrole,2,4-dimethylpyrrole, 2,5-dimethylpyrrole, and N-methylpyrrole), oxazolederivatives (e.g., oxazole and isooxazole), thiazole derivatives (e.g.,thiazole and isothiazole), imidazole derivatives (e.g., imidazole,4-methylimidazole, and 4-methyl-2-phenylimidazole), pyrazolederivatives, furazan derivatives, pyrroline derivatives (e.g., pyrrolineand 2-methyl-1-pyrroline), pyrrolidine derivatives (e.g., pyrrolidine,N-methylpyrrolidine, pyrrolidinone, and N-methylpyrrolidone),imidazoline derivatives, imidazolidine derivatives, pyridine derivatives(e.g., pyridine, methylpyridine, ethylpyridine, propylpyridine,butylpyridine, 4-(1-butylpentyl)pyridine, dimethylpyridine,trimethylpyridine, triethylpyridine, phenylpyridine,3-methyl-2-phenylpyridine, 4-tert-butylpyridine, diphenylpyridine,benzylpyridine, methoxypyridine, butoxypyridine, dimethoxypyridine,4-pyrrolidinopyridine, 2-(1-ethylpropyl)pyridine, aminopyridine, anddimethylaminopyridine), pyridazine derivatives, pyrimidine derivatives,pyrazine derivatives, pyrazoline derivatives, pyrazolidine derivatives,piperidine derivatives, piperazine derivatives, morpholine derivatives,indole derivatives, isoindole derivatives, 1H-indazole derivatives,indoline derivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl groupinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g. nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable nitrogen-containing compounds having sulfonyl group include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, and alcoholicnitrogen-containing compounds include 2-hydroxypyridine, aminocresol,2,4-quinolinediol, 3-indolemethanol hydrate, monoethanolamine,diethanolamine, triethanolamine, N-ethyldiethanolamine,N,N-diethylethanolamine, triisopropanolamine, 2,2′-iminodiethanol,2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol,4-(2-hydroxyethyl)morpholine, 2-(2-hydroxyethyl)pyridine,1-(2-hydroxyethyl)piperazine, 1-[2-(2-hydroxyethoxy)ethyl]piperazine,piperidine ethanol, 1-(2-hydroxyethyl)pyrrolidine,1-(2-hydroxyethyl)-2-pyrrolidinone, 3-piperidino-1,2-propanediol,3-pyrrolidino-1,2-propanediol, 8-hydroxyjulolidine, 3-quinuclidinol,3-tropanol, 1-methyl-2-pyrrolidine ethanol, 1-aziridine ethanol,N-(2-hydroxyethyl)phthalimide, and N-(2-hydroxyethyl)isonicotinamide.Examples of suitable amide derivatives include formamide,N-methylformamide, N,N-dimethylformamide, acetamide, N-methylacetamide,N,N-dimethylacetamide, propionamide, benzamide, and1-cyclohexylpyrrolidone. Suitable imide derivatives include phthalimide,succinimide, and maleimide. Suitable carbamate derivatives includeN-t-butoxycarbonyl-N,N-dicyclohexylamine,N-t-butoxycarbonylbenzimidazole and oxazolidinone.

In addition, organic nitrogen-containing compounds of the followinggeneral formula (B)-1 may also be included alone or in admixture.N(X)_(n)(Y)_(3-n)  (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independentlyhydrogen or a straight, branched or cyclic alkyl group of 1 to 20 carbonatoms which may contain an ether or hydroxyl group; and side chain X isindependently selected from groups of the following general formulas(X1) to (X3), and two or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl, ether,ester group or lactone ring; R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms; and R³⁰⁶ is a straight,branched or cyclic alkyl group of 1 to 20 carbon atoms, which maycontain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (B)-1 includetris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine,tris{2-(2-methoxyethoxymethoxy)ethyl}amine,tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine,tris{2-(1-ethoxypropoxy)ethyl}amine,tris[2-(2-(2-hydroxyethoxy)ethoxy)ethyl]amine,4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane, 1-aza-12-crown-4,1-aza-15-crown-5, 1-aza-18-crown-6, tris(2-formyloxyethyl)amine,tris(2-acetoxyethyl)amine, tris(2-propionyloxyethyl)amine,tris(2-butyryloxyethyl)amine, tris(2-isobutyryloxyethyl)amine,tris(2-valeryloxyethyl)amine, tris(2-pivaloyloxyethyl)amine,N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,tris(2-methoxycarbonyloxyethyl)amine,tris(2-tert-butoxycarbonyloxyethyl)amine,tris[2-(2-oxopropoxy)ethyl]amine,tris[2-(methoxycarbonylmethyl)oxyethyl]amine,tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,tris(2-methoxycarbonylethyl)amine, tris(2-ethoxycarbonylethyl)amine,N,N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,N,N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,N,N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,N,N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxycarbonyl]ethylamine,N,N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,N,N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)-ethylamine,N,N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)-ethylamine,N,N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,N-methyl-bis(2-acetoxyethyl)amine, N-ethyl-bis(2-acetoxyethyl)amine,N-methyl-bis(2-pivaloyloxyethyl)amine,N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,tris(methoxycarbonylmethyl)amine, tris(ethoxycarbonylmethyl)amine,N-butyl-bis(methoxycarbonylmethyl)amine,N-hexyl-bis(methoxycarbonylmethyl)amine, andβ-(diethylamino)-δ-valerolactone.

Also useful are one or more organic nitrogen-containing compounds havingcyclic structure represented by the following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branchedalkylene group of 2 to 20 carbon atoms which may contain one or morecarbonyl, ether, ester or sulfide groups.

Illustrative examples of the organic nitrogen-containing compoundshaving formula (B)-2 include 1-[2-(methoxymethoxy)ethyl]pyrrolidine,1-[2-(methoxymethoxy)ethyl]piperidine,4-[2-(methoxymethoxy)ethyl]morpholine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine, 2-(1-pyrrolidinyl)ethylacetate, 2-piperidinoethyl acetate, 2-morpholinoethyl acetate,2-(1-pyrrolidinyl)ethyl formate, 2-piperidinoethyl propionate,2-morpholinoethyl acetoxyacetate, 2-(1-pyrrolidinyl)ethylmethoxyacetate, 4-[2-(methoxycarbonyloxy)ethyl]morpholine,1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine, methyl3-(1-pyrrolidinyl)propionate, methyl 3-piperidinopropionate, methyl3-morpholinopropionate, methyl 3-(thiomorpholino)propionate, methyl2-methyl-3-(1-pyrrolidinyl)propionate, ethyl 3-morpholinopropionate,methoxycarbonylmethyl 3-piperidinopropionate, 2-hydroxyethyl3-(1-pyrrolidinyl)propionate, 2-acetoxyethyl 3-morpholinopropionate,2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,tetrahydrofurfuryl 3-morpholinopropionate, glycidyl3-piperidinopropionate, 2-methoxyethyl 3-morpholinopropionate,2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate, butyl3-morpholinopropionate, cyclohexyl 3-piperidinopropionate,α-(1-pyrrolidinyl)methyl-γ-butyrolactone, β-piperidino-γ-butyrolactone,β-morpholino-δ-valerolactone, methyl 1-pyrrolidinylacetate, methylpiperidinoacetate, methyl morpholinoacetate, methylthiomorpholinoacetate, ethyl 1-pyrrolidinylacetate, 2-methoxyethylmorpholinoacetate, 2-morpholinoethyl 2-methoxyacetate, 2-morpholinoethyl2-(2-methoxyethoxy)acetate, 2-morpholinoethyl2-[2-(2-methoxyethoxy)ethoxy]acetate, 2-morpholinoethyl hexanoate,2-morpholinoethyl octanoate, 2-morpholinoethyl decanoate,2-morpholinoethyl laurate, 2-morpholinoethyl myristate,2-morpholinoethyl palmitate, and 2-morpholinoethyl stearate.

Also, one or more organic nitrogen-containing compounds having cyanogroup represented by the following general formulae (B)-3 to (B)-6 maybe blended.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are eachindependently a straight or branched alkylene group of 1 to 4 carbonatoms.

Illustrative examples of the organic nitrogen-containing compoundshaving cyano represented by formulae (B)-3 to (B)-6 include3-(diethylamino)propiononitrile,N,N-bis(2-hydroxyethyl)-3-aminopropiononitrile,N,N-bis(2-acetoxyethyl)-3-aminopropiononitrile,N,N-bis(2-formyloxyethyl)-3-aminopropiononitrile,N,N-bis(2-methoxyethyl)-3-aminopropiononitrile,N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile, methylN-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate, methylN-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiononitrile,N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiononitrile,N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,N,N-bis(2-cyanoethyl)-3-aminopropiononitrile, diethylaminoacetonitrile,N,N-bis(2-hydroxyethyl)aminoacetonitrile,N,N-bis(2-acetoxyethyl)aminoacetonitrile,N,N-bis(2-formyloxyethyl)aminoacetonitrile,N,N-bis(2-methoxyethyl)aminoacetonitrile,N,N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile, methylN-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate, methylN-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate, methylN-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,N,N-bis(cyanomethyl)aminoacetonitrile, 1-pyrrolidinepropiononitrile,1-piperidinepropiononitrile, 4-morpholinepropiononitrile,1-pyrrolidineacetonitrile, 1-piperidineacetonitrile,4-morpholineacetonitrile, cyanomethyl 3-diethylaminopropionate,cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, cyanomethylN,N-bis(2-methoxyethyl)-3-aminopropionate, cyanomethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, 2-cyanoethyl3-diethylaminopropionate, 2-cyanoethylN,N-bis(2-hydroxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-acetoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-formyloxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis(2-methoxyethyl)-3-aminopropionate, 2-cyanoethylN,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate, cyanomethyl1-pyrrolidinepropionate, cyanomethyl 1-piperidinepropionate, cyanomethyl4-morpholinepropionate, 2-cyanoethyl 1-pyrrolidinepropionate,2-cyanoethyl 1-piperidinepropionate, and 2-cyanoethyl4-morpholinepropionate.

Also included are organic nitrogen-containing compounds having animidazole structure and a polar functional group, represented by thegeneral formula (B)-7.

Herein, R³¹⁰ is a straight, branched or cyclic alkyl group of 2 to 20carbon atoms bearing at least one polar functional group selected fromamong hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano andacetal groups; R³¹¹, R³¹² and R³¹³ are each independently a hydrogenatom, a straight, branched or cyclic alkyl group, aryl group or aralkylgroup having 1 to 10 carbon atoms.

Also included are organic nitrogen-containing compounds having abenzimidazole structure and a polar functional group, represented by thegeneral formula (B)-8.

Herein, R³¹⁴ is a hydrogen atom, a straight, branched or cyclic alkylgroup, aryl group or aralkyl group having 1 to 10 carbon atoms. R³¹⁵ isa polar functional group-bearing, straight, branched or cyclic alkylgroup of 1 to 20 carbon atoms, and the alkyl group contains as the polarfunctional group at least one group selected from among ester, acetaland cyano groups, and may additionally contain at least one groupselected from among hydroxyl, carbonyl, ether, sulfide and carbonategroups.

Further included are heterocyclic nitrogen-containing compounds having apolar functional group, represented by the general formulae (B)-9 and(B)-10.

Herein, A is a nitrogen atom or ≡C—R³²², B is a nitrogen atom or≡C—R³²³, R³¹⁶ is a straight, branched or cyclic alkyl group of 2 to 20carbon atoms bearing at least one polar functional group selected fromamong hydroxyl, carbonyl, ester, ether, sulfide, carbonate, cyano andacetal groups; R³¹⁷, R³¹⁸, R³¹⁹ and R³²⁰ are each independently ahydrogen atom, a straight, branched or cyclic alkyl group or aryl grouphaving 1 to 10 carbon atoms, or a pair of R³¹⁷ and R³¹⁶ and a pair ofR³¹⁹ and R³²⁰, taken together, may form a benzene, naphthalene orpyridine ring; R³²¹ is a hydrogen atom, a straight, branched or cyclicalkyl group or aryl group having 1 to 10 carbon atoms; R³²² and R³²³each are a hydrogen atom, a straight, branched or cyclic alkyl group oraryl group having 1 to 10 carbon atoms, or a pair of R³²¹ and R³²³,taken together, may form a benzene or naphthalene ring.

Also included are organic nitrogen-containing compounds of aromaticcarboxylic ester structure having the general formulae (B1)-11 to(B)-14.

Herein R³²⁴ is a C₆-C₂₀ aryl group or C₄-C₂₀ hetero-aromatic group, inwhich some or all of hydrogen atoms may be replaced by halogen atoms,straight, branched or cyclic C₁-C₂₀ alkyl groups, C₆-C₂₀ aryl groups,C₇-C₂₀ aralkyl groups, C₁-C₁₀ alkoxy groups, C₁-C₁₀ acyloxy groups orC₁-C₁₀ alkylthio groups. R³²⁵ is CO₂R³²⁶, OR³²⁷ or cyano group. R³²⁶ isa C₁-C₁₀ alkyl group, in which some methylene groups may be replaced byoxygen atoms. R³²⁷ is a C₁-C₁₀ alkyl or acyl group, in which somemethylene groups may be replaced by oxygen atoms. R³²⁸ is a single bond,methylene, ethylene, sulfur atom or —O(CH₂CH₂O)_(n)— group wherein n is0, 1, 2, 3 or 4. R³²⁹ is hydrogen, methyl, ethyl or phenyl. X is anitrogen atom or CR³³⁰. Y is a nitrogen atom or CR³³¹. Z is a nitrogenatom or CR³³². R³³⁰, R³³¹ and R³³² are each independently hydrogen,methyl or phenyl. Alternatively, a pair of R³³⁰ and R³³¹ or a pair ofR³³¹ and R³³² may bond together to form a C₆-C₂₀ aromatic ring or C₂-C₂₀hetero-aromatic ring.

Further included are organic nitrogen-containing compounds of7-oxanorbornane-2-carboxylic ester structure having the general formula(B)-15.

Herein R³³³ is hydrogen or a straight, branched or cyclic C₁-C₁₀ alkylgroup. R³³⁴ and R³³⁵ are each independently a C₁-C₂₀ alkyl group, C₆-C₂₀aryl group or C₇-C₂₀ aralkyl group, which may contain one or more polarfunctional groups selected from among ether, carbonyl, ester, alcohol,sulfide, nitrile, amine, imine, and amide and in which some hydrogenatoms may be replaced by halogen atoms. R³³⁴ and R³³⁵, taken together,may form a heterocyclic or hetero-aromatic ring of 2 to 20 carbon atoms.

The organic nitrogen-containing compounds may be used alone or inadmixture of two or more. The organic nitrogen-containing compound ispreferably formulated in an amount of 0.001 to 2 parts, and especially0.01 to 1 part by weight, per 100 parts by weight of the base resin. Atleast 0.001 phr of the nitrogen-containing compound achieves a desiredaddition effect whereas up to 2 phr minimizes a risk of loweringsensitivity.

Surfactant

The resist composition of the invention may include a surfactant whichis commonly used for improving the coating characteristics. It may beadded in conventional amounts so long as this does not compromise theobjects of the invention.

Nonionic surfactants are preferred, examples of which includeperfluoroalkylpolyoxyethylene ethanols, fluorinated alkyl esters,perfluoroalkylamine oxides, perfluoroalkyl EO-addition products, andfluorinated organosiloxane compounds. Useful surfactants arecommercially available under the trade names Fluorad FC-430 and FC-431from Sumitomo 3M, Ltd., Surflon S-141, S-145, KH-10, KH-20, KH-30 andKH-40 from Asahi Glass Co., Ltd., Unidyne DS-401, DS-403 and DS-451 fromDaikin Industry Co., Ltd., Megaface F-8151 from Dai-Nippon Ink &Chemicals, Inc., and X-70-092 and X-70-093 from Shin-Etsu Chemical Co.,Ltd. Preferred surfactants are Fluorad FC-430 from Sumitomo 3M, Ltd.,KH-20 and KH-30 from Asahi Glass Co., Ltd., and X-70-093 from Shin-EtsuChemical Co., Ltd.

Also, if desired, other components including dissolution regulators,carboxylic acid compounds and acetylene alcohol derivatives may be addedto the resist composition of the invention. Optional components may beadded in conventional amounts so long as this does not compromise theobjects of the invention.

Dissolution Regulator

The dissolution regulator which can be added to the resist compositionis a compound having on the molecule at least two phenolic hydroxylgroups, in which an average of from 0 to 100 mol % of all the hydrogenatoms on the phenolic hydroxyl groups are replaced by acid labile groupsor a compound having on the molecule at least one carboxyl group, inwhich an average of 50 to 100 mol % of all the hydrogen atoms on thecarboxyl groups are replaced by acid labile groups, both the compoundshaving a weight average molecular weight within a range of 100 to 1,000,and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mold, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having at least one carboxyl group includethose of formulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl group, for example, hydrogen, methyl,ethyl, butyl, propyl, ethynyl and cyclohexyl.

R²⁰³ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl group,or —(R²⁰⁷)_(h)—COOH wherein R²⁰⁷ is a straight or branched C₁-C₁₀alkylene and h is 0 or 1, for example, those exemplified for R²⁰¹ andR²⁰² and —COOH and —CH₂COOH.

R²⁰⁴ is —(CH₂)_(i)— wherein i=2 to 10, C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom, for example, ethylene,phenylene, carbonyl, sulfonyl, oxygen atom or sulfur atom.

R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom, for example, methylene and thoseexemplified for R²⁰⁴.

R²⁰⁶ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl group,or a phenyl or naphthyl group having hydroxyl substituted thereon, forexample, hydrogen, methyl, ethyl, butyl, propyl, ethynyl, cyclohexyl,hydroxyl-substituted phenyl, and hydroxyl-substituted naphthyl.

R²⁰⁸ is hydrogen or hydroxyl.

The letter j is an integer from 0 to 5; u and h are each 0 or 1; s, t,s′, t′, s″, and t″ are each numbers which satisfy s+t=8, s′+t′=5, ands″+t″=4, and are such that each phenyl skeleton has at least onehydroxyl group; and a is a number such that the compounds of formula(D8) or (D9) have a weight average molecular weight of from 100 to1,000.

Exemplary acid labile groups on the dissolution regulator include avariety of such groups, typically groups of the general formulae (L1) to(L4), tertiary alkyl groups of 4 to 20 carbon atoms, trialkylsilylgroups in which each of the alkyls has 1 to 6 carbon atoms, and oxoalkylgroups of 4 to 20 carbon atoms. Examples of the respective groups are aspreviously described.

The dissolution regulator may be formulated in an amount of 0 to 50parts, preferably 0 to 40 parts, and more preferably 0 to 30 parts byweight, per 100 parts by weight of the base resin, and may be usedsingly or as a mixture of two or more thereof. Up to 50 phr of thedissolution regulator minimizes a risk of slimming the patterned filmand reducing the resolution.

The dissolution regulator can be synthesized by introducing acid labilegroups into a compound having phenolic hydroxyl or carboxyl groups inaccordance with an organic chemical formulation.

In the resist composition, a carboxylic acid compound may be blended.Exemplary, non-limiting carboxylic acid compounds include one or morecompounds selected from Groups I and II below. Including this compoundimproves the PED stability of the resist and ameliorates edge roughnesson nitride film substrates.

Group 1:

Compounds in which some or all of the hydrogen atoms on the phenolichydroxyl groups of the compounds of general formulas (A1) to (A10) beloware replaced by —R⁴⁰⁰—COOH (wherein R⁴⁰¹ is a straight or branchedalkylene of 1 to 10 carbon atoms), and in which the molar ratio C/(C+D)of phenolic hydroxyl groups (C) to ≡C—COOH groups (D) in the molecule isfrom 0.1 to 1.0.

In these formulas, R⁴⁰² and R⁴⁰³ are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl; R⁴⁰⁴ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl, or a —(R⁴⁰⁹)_(h)—COOR′ group (R′ beinghydrogen or —R⁴⁰⁹—COOH); R⁴⁰⁵ is —(CH₂)_(i)— (wherein i is 2 to 10), aC₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom;R⁴⁰⁶ is a C₁-C₁₀ alkylene, a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom; R⁴⁰⁷ is hydrogen, a straight or branchedC₁-C₈ alkyl or alkenyl, or a hydroxyl-substituted phenyl or naphthyl;R⁴⁰⁸ is hydrogen or methyl; R⁴⁰⁹ is a straight or branched C₁-C₁₀alkylene; R⁴¹⁰ is hydrogen, a straight or branched C₁-C₈ alkyl oralkenyl, or a —R¹¹¹—COOH group; R⁴¹¹ is a straight or branched C₁-C₁₀alkylene; the letter j is an integer from 0 to 3; s1, t1, s2, t2, s3,t3, s4, and t4 are each numbers which satisfy s1+t1=8, s2+t2=5, s3+t3=4,and s4+t4=6, and are such that each phenyl structure has at least onehydroxyl group; u is a number from 1 to 4, h is a number from 1 to 4; κis a number such that the compound of formula (A6) may have a weightaverage molecular weight of 1,000 to 5,000; and λ is a number such thatthe compound of formula (A7) may have a weight average molecular weightof 1,000 to 10,000.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above; R⁴¹² ishydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5≧0, t5≧0,and s5+t5=5; and h is a number from 1 to 4.

Illustrative, non-limiting examples of the compound having a carboxylgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the—CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, κand λ are as defined above.

The compound having a ≡C—COOH group in the molecule is added in anamount ranging from 0 to 5 parts, preferably 0.1 to 5 parts, morepreferably 0.1 to 3 parts, even more preferably 0.1 to 2 parts byweight, per 100 parts by weight of the base resin. Up to 5 phr of thecompound minimizes a risk of the resist composition reducing itsresolution.

The resist composition of the invention may additionally include anacetylene alcohol derivative. Preferred acetylene alcohol derivativesare those having the general formula (S1) or (S2) below.

In the formulas, R⁵⁰¹, R⁵⁰², R⁵⁰³, R⁵⁰⁴, and R⁵⁰⁵ are each hydrogen or astraight, branched or cyclic C₁-C₈ alkyl; and X and Y are each 0 or apositive number, satisfying 0≦X≦30, 0≦Y≦30, and 0≦X+Y≦40.

Preferable examples of the acetylene alcohol derivative include Surfynol61, Surfynol 82, Surfynol 104, Surfynol 104E, Surfynol 104H, Surfynol104A, Surfynol TG, Surfynol PC, Surfynol 440, Surfynol 465, and Surfynol485 from Air Products and Chemicals Inc., and Surfynol E1004 fromNisshin Chemical Industry K.K.

The acetylene alcohol derivative is preferably added in an amount of0.01 to 2% by weight, and more preferably 0.02 to 1% by weight, based onthe weight of the resist composition. At least 0.01 wt % is fullyeffective in improving the coating operation and shelf stability. Up to2 wt % minimizes a risk of the resist composition reducing itsresolution.

If desired, crosslinkers commonly used in negative resist or otherapplications may be added to the resist composition. Suitablecrosslinkers include compounds having at least two hydroxymethyl,alkoxymethyl, epoxy or vinyl ether groups in a molecule. Exemplarycrosslinkers are substituted glycoluril derivatives, urea derivatives,and hexa(methoxymethyl)melamine compounds. Examples includeN,N,N′,N′-tetramethoxymethylurea, hexamethoxymethylmelamine,tetrahydroxymethyl-substituted glycoluril, tetraalkoxymethyl-substitutedglycoluril compounds such as tetramethoxymethylglycoluril, andcondensates of phenolic compounds such as substituted or unsubstitutedbis(hydroxymethylphenol) compounds and bisphenol A with epichlorohydrin.Especially preferred crosslinkers include1,3,4,6-tetraalkoxymethylglycolurils such as1,3,4,6-tetramethoxymethylglycoluril, as well as1,3,4,6-tetrahydroxymethylglycoluril, 2,6-dihydroxymethyl-p-cresol,2,6-dihydroxymethylphenol, 2,2′,6,6′-tetrahydroxymethyl-bisphenol A,1,4-bis[2-(2-hydroxypropyl)]benzene, N,N,N′,N′-tetramethoxymethylurea,and hexamethoxymethylmelamine.

In the resist composition, the crosslinker is added in any desiredamount, preferably in an amount of 1 to 25 parts by weight, morepreferably 5 to 20 parts by weight per 100 parts by weight of the baseresin. The crosslinkers may be used alone or in admixture of two ormore.

Process

The pattern forming process of the invention involves the steps of (1)applying the resist composition onto a substrate to form a coating, (2)heat treating the coating and exposing it to high-energy radiation, and(3) developing the exposed coating with a developer. Preferably thehigh-energy radiation has a wavelength in the range of 180 to 250 nm.

The step of exposing the resist coating to high-energy radiation may bean immersion lithography step of directing radiation via a liquid and becarried out, for example, by using radiation having a wavelength of 180to 250 nm, holding a liquid between the projection lens and theresist-coated substrate and directing the radiation to the substrate viathe liquid. The liquid used in the immersion lithography is typicallywater.

Pattern formation using the resist composition of the invention may becarried out by a known lithographic technique. For example, the resistcomposition is applied onto a substrate such as a silicon wafer by spincoating or the like. The coating is then pre-baked on a hot plate at 60to 150° C. for 1 to 10 minutes, and preferably at 80 to 140° C. for 1 to5 minutes to form a resist film having a thickness of 0.1 to 2.0 μm.

Once the resist film is formed, light exposure in water is carried outby KrF or ArF immersion lithography. This is followed by post-exposurebake (PEB) and development in an alkaline developer for 10 to 300seconds. An aqueous solution of 2.38 wt % tetramethylammonium hydroxide(TMAH), which is commonly used as the alkaline developer, is used hereinwhereby the resist film is developed. Sometimes water is left on theresist film prior to PEB. If PEB is performed in the presence ofresidual water, water can penetrate into the resist coating to suck upthe acid in the resist, impeding pattern formation. To fully remove thewater on the resist film prior to PEB, the water on the resist should bedried or recovered by suitable means, for example, spin drying prior toPEB, purging of the film surface with dry air or nitrogen, or optimizingthe water recovery nozzle configuration or process on a stage after theexposure. Additionally, the resist film of the invention has high waterrepellency and thus advantageously facilitates water recovery.

The type of photoresist material is not particularly limited whilepolymers of formulae (R1) and (R2) as defined above are advantageouslyused as the base resin. The photoresist may be either positive ornegative working and also either a monolayer resist of conventionalhydrocarbon or a bilayer resist containing silicon atoms and the like.For KrF lithography resist materials, the preferred base resins arepolyhydroxystyrene or polyhydroxystyrene-(meth)acrylate copolymers inwhich some or all hydrogen atoms of hydroxyl or carboxyl groups arereplaced by acid labile groups.

For ArF lithography resist materials, the base resin must have anaromatic-free structure. Illustrative polymers include polyacrylic acidand derivatives thereof, norbornene derivative-maleic anhydridealternating copolymers and ternary or quaternary copolymers thereof withpolyacrylic acid or derivatives thereof, tetracyclododecenederivative-maleic anhydride alternating copolymers and ternary orquaternary copolymers thereof with polyacrylic acid or derivativesthereof, norbornene derivative-maleimide alternating copolymers andternary or quaternary copolymers thereof with polyacrylic acid orderivatives thereof, tetracyclododecene derivative-maleimide alternatingcopolymers and ternary or quaternary copolymers thereof with polyacrylicacid or derivatives thereof, and polynorbornene and metathesisring-opening polymers, and a combination comprising at least one of theforegoing polymers.

The photoresist film formed from the resist composition of the inventionexhibits a good barrier property against water and prevents thephotoresist material from being dissolved or leached in water. It thuseliminates a need for a protective coating in the immersion lithography,contributing to a reduction of the cost required in the formation ofprotective coating or the like. Also the photoresist film has so large areceding contact angle with water that few droplets are left on theresist film surface after immersion lithography scanning, minimizingdefective pattern formation which is caused by residual droplets on thefilm surface.

When used for mask blanks, the resist compositions of the inventionoften include novolac and hydroxystyrene base resins. Those resins inwhich hydroxyl groups are substituted by acid labile groups are used forpositive resists while these resins in combination with crosslinkers areused for negative resists. Base polymers which can be used hereininclude copolymers of hydroxystyrene with one or more of (meth)acrylicderivatives, styrenes, vinyl naphthalenes, vinyl anthracenes, vinylpyrenes, hydroxyvinyl naphthalenes, hydroxyvinyl anthracenes, indenes,hydroxyindenes, acenaphthylenes, and norbornadienes. Suitablecrosslinkers include melamine compounds, guanamine compounds, glycolurilcompounds and urea compounds having substituted thereon at least onegroup selected from methylol, alkoxymethyl and acyloxymethyl groups, andepoxy compounds, thioepoxy compounds, isocyanate compounds, azidecompounds and compounds having a double bond such as an alkenyl ethergroup. These compounds may be used as an additive or introduced aspendant groups on polymer side chains. Compounds having a hydroxy groupare also useful as the crosslinker.

Where the inventive polymer is used as an additive to a resistcomposition for use with mask blanks, the inventive polymer is added tothe above-mentioned base resin to form a resist solution, which iscoated on a mask blank substrate of SiO₂, Cr, CrO, CrN, MoSi or thelike. By further forming a SOG film and an organic undercoat filmbetween the photoresist and the blank substrate, there is provided athree-layer structure which is also acceptable herein. Once the resistfilm is formed, the structure is irradiated with electron beam in vacuumusing an electron beam exposure system. The irradiation is followed bypost-exposure baking (PEB) and development in an alkaline developer for10 to 300 seconds.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. The abbreviations used herein are GPC for gelpermeation chromatography, NMR for nuclear magnetic resonance, Mw forweight average molecular weight, Mn for number average molecular weight,and Mw/Mn for molecular weight dispersity. Mw and Mn are determined byGPC versus polystyrene standards. All parts are by weight (pbw).

Preparation of Polymers

Additive polymers to be added to resist compositions were prepared bycombining monomers, effecting copolymerization reaction in isopropylalcohol as a solvent, pouring the polymerization solution into hexanefor crystallization, washing the polymer with hexane, isolating anddrying. The resulting polymers were analyzed for composition by ¹H-NMRand for Mw and Mw/Mn by GPC.

Polymer 1

Mw=7,300

Mw/Mn=1.67

Polymer 2

Mw=7,400

Mw/Mn=1.61

Polymer 3

Mw=6,100

Mw/Mn=1.68

Polymer 4

Mw=8,000

Mw/Mn=1.80

Polymer 5

Mw=8,100

Mw/Mn=1.74

Polymer 6

Mw=8,300

Mw/Mn=1.79

Polymer 7

Mw=7,800

Mw/Mn=1.78

Polymer 8

Mw=7,600

Mw/Mn=1.69

Polymer 9

Mw=7,900

Mw/Mn=1.82

Polymer 10

Mw=7,100

Mw/Mn=1.81

Polymer 11

Mw=7,300

Mw/Mn=1.86

Polymer 12

Mw=7,900

Mw/Mn=1.83

Polymer 13

Mw=7,800

Mw/Mn=1.81

Reference Polymer 1

Mw=7,600

Mw/Mn=1.71

Reference Polymer 2

Mw=8,100

Mw/Mn=1.72

Reference Polymer 3

Mw=8,600

Mw/Mn=1.77

Preparation of Resist Compositions

Resist compositions, designated Resists 1 and 2, were prepared bycombining and dissolving a base resin, a photoacid generator, and abasic compound in an organic solvent in accordance with the recipe shownbelow, and filtering through a Teflon® filter having a pore size of 0.2

Resist 1

Mixing Composition:

Base Resin 1 100 pbw PAG 5 pbw Basic compound 1 pbw Organic solvent 1800pbw

Base Resin 1 has the following structural formula.

-   -   Mw 7,600    -   Mw/Mn=1.76

-   PAG: triphenylsulfonium nonafluorobutanesulfonate

-   Basic compound (or quencher):    2-(2-methoxyethoxymethoxy)ethylmorpholine

-   Organic solvent: 1-methoxyisopropyl acetate    Resist 2

Mixing Composition:

Base Resin 2 100 pbw PAG 7 pbw Basic compound 0.8 pbw Organic solvent 11330 pbw Organic solvent 2 570 pbw

Base Resin 2 has the following structural formula.

-   -   Mw=5,700    -   Mw/Mn=1.69

-   PAG: 4-t-butoxyphenyldiphenylsulfonium    1,1,3,3,3-pentafluoro-2-benzoyloxypropanesulfonate

-   Basic compound (or quencher): 2-cyclohexylcarboxyethylmorpholine

-   Organic solvent 1: 1-methoxyisopropyl acetate

-   Organic solvent 2: cyclohexanone

Resist coating solutions (Examples 1-19 and Comparative Examples 1-5)were prepared by compounding the resist composition as a matrix with oneof the above-prepared polymers (Polymers 1 to 13) in a suitableproportion. Table 1 shows a combination of the additive polymer and thematrix resist composition and a proportion. It is noted that theproportion of the additive polymer is expressed in parts by weight per100 parts by weight of the base resin in the matrix resist composition.

TABLE 1 Matrix resist Resist solution composition Additive polymer(amount) Example 1 Resist 1 Polymer 1 (5 pbw) Example 2 Resist 1 Polymer2 (5 pbw) Example 3 Resist 1 Polymer 3 (5 pbw) Example 4 Resist 1Polymer 4 (5 pbw) Example 5 Resist 1 Polymer 5 (5 pbw) Example 6 Resist1 Polymer 6 (5 pbw) Example 7 Resist 2 Polymer 1 (5 pbw) Example 8Resist 2 Polymer 2 (5 pbw) Example 9 Resist 2 Polymer 3 (5 pbw) Example10 Resist 2 Polymer 4 (5 pbw) Example 11 Resist 2 Polymer 5 (5 pbw)Example 12 Resist 2 Polymer 6 (5 pbw) Example 13 Resist 2 Polymer 7 (5pbw) Example 14 Resist 2 Polymer 8 (5 pbw) Example 15 Resist 2 Polymer 9(5 pbw) Example 16 Resist 2 Polymer 10 (5 pbw) Example 17 Resist 2Polymer 11 (5 pbw) Example 18 Resist 2 Polymer 12 (5 pbw) Example 19Resist 2 Polymer 13 (5 pbw) Comparative Example 1 Resist 1 — ComparativeExample 2 Resist 2 — Comparative Example 3 Resist 2 Reference polymer 1(5 pbw) Comparative Example 4 Resist 2 Reference polymer 2 (5 pbw)Comparative Example 5 Resist 2 Reference polymer 3 (5 pbw)Measurement of Receding Contact Angle and Sliding Angle

The resist solutions (Examples 1-19 and Comparative Examples 1-5) werespin coated on silicon substrates, then baked at 120° C. for 60 secondsto give photoresist films having a thickness of 200 nm.

An inclination contact angle meter Drop Master 500 by Kyowa InterfaceScience Co., Ltd. was used. The wafer with the resist film was kepthorizontal, and 50 μL of ultrapure water was dropped on the resist filmto form a droplet. While the wafer was gradually inclined, the angle(sliding angle) at which the droplet started sliding down was determinedas well as receding contact angle. The results are shown in Table 2.

TABLE 2 Receding Matrix Sliding contact resist Additive polymer angleangle Resist solution composition (amount) (°) (°) Example 1 Resist 1Polymer 1 (5 pbw) 17 68 Example 2 Resist 1 Polymer 2 (5 pbw) 17 69Example 3 Resist 1 Polymer 3 (5 pbw) 16 72 Example 4 Resist 1 Polymer 4(5 pbw) 17 71 Example 5 Resist 1 Polymer 5 (5 pbw) 18 67 Example 6Resist 1 Polymer 6 (5 pbw) 18 67 Example 7 Resist 2 Polymer 1 (5 pbw) 1566 Example 8 Resist 2 Polymer 2 (5 pbw) 16 66 Example 9 Resist 2 Polymer3 (5 pbw) 14 69 Example 10 Resist 2 Polymer 4 (5 pbw) 15 70 Example 11Resist 2 Polymer 5 (5 pbw) 16 65 Example 12 Resist 2 Polymer 6 (5 pbw)16 64 Example 13 Resist 2 Polymer 7 (5 pbw) 13 76 Example 14 Resist 2Polymer 8 (5 pbw) 16 73 Example 15 Resist 2 Polymer 9 (5 pbw) 16 75Example 16 Resist 2 Polymer 10 (5 pbw) 15 73 Example 17 Resist 2 Polymer11 (5 pbw) 15 78 Example 18 Resist 2 Polymer 12 (5 pbw) 16 79 Example 19Resist 2 Polymer 13 (5 pbw) 16 80 Comparative Example 1 Resist 1 — 23 55Comparative Example 2 Resist 2 — 18 51 Comparative Example 3 Resist 2Reference Polymer 1 (5 pbw) 21 60 Comparative Example 4 Resist 2Reference Polymer 2 (5 pbw) 8 88 Comparative Example 5 Resist 2Reference Polymer 3 (5 pbw) 14 72

A smaller sliding angle indicates an easier flow of water on the resistfilm. A larger receding contact angle indicates that fewer liquiddroplets are left during high-speed scan exposure. As is evident fromTable 2, resist solutions having the inventive polymers compoundedtherein (Examples 1 to 19) form photoresist-films which have a largerreceding contact angle and a smaller sliding angle than thosephotoresist films without the inventive polymer (Comparative Examples 1,2). It is demonstrated that inclusion of the inventive polymer achievesa drastic improvement in the receding contact angle of photoresist filmwithout adversely affecting the sliding angle.

Measurement of Leach-Outs

The resist solutions (Examples 1-19 and Comparative Examples 1-5) werespin coated on silicon substrates, then baked at 120° C. for 60 secondsto give photoresist films having a thickness of 200 nm. Using an ArFscanner S305B (Nikon Corp.), the entire surface of the photoresist filmwas irradiated through an open frame at an energy dose of 50 mJ/cm².Then a true circle ring of Teflon® having an inner diameter of 10 cm wasplaced on the resist film, 10 mL of deionized water was carefullyinjected inside the ring, and the resist film was kept in contact withwater at room temperature for 60 seconds. Thereafter, the water wasrecovered, and a concentration of PAG anion in the water was measured byan LC-MS analyzer (Agilent). The anion concentration measured indicatesan amount of anions leached out for 60 seconds. The results are shown inTable 3.

TABLE 3 Matrix Anion resist Additive polymer leach-out Resist solutioncomposition (amount) (ppb) Example 1 Resist 1 Polymer 1 (5 pbw) 8Example 2 Resist 1 Polymer 2 (5 pbw) 7 Example 3 Resist 1 Polymer 3 (5pbw) 5 Example 4 Resist 1 Polymer 4 (5 pbw) 7 Example 5 Resist 1 Polymer5 (5 pbw) 10 Example 6 Resist 1 Polymer 6 (5 pbw) 9 Example 7 Resist 2Polymer 1 (5 pbw) 12 Example 8 Resist 2 Polymer 2 (5 pbw) 10 Example 9Resist 2 Polymer 3 (5 pbw) 9 Example 10 Resist 2 Polymer 4 (5 pbw) 10Example 11 Resist 2 Polymer 5 (5 pbw) 14 Example 12 Resist 2 Polymer 6(5 pbw) 11 Example 13 Resist 2 Polymer 7 (5 pbw) 3 Example 14 Resist 2Polymer 8 (5 pbw) 8 Example 15 Resist 2 Polymer 9 (5 pbw) 5 Example 16Resist 2 Polymer 10 (5 pbw) 7 Example 17 Resist 2 Polymer 11 (5 pbw) 4Example 18 Resist 2 Polymer 12 (5 pbw) 3 Example 19 Resist 2 Polymer 13(5 pbw) 3 Comparative Example 1 Resist 1 — 25 Comparative Example 2Resist 2 — 36 Comparative Example 3 Resist 2 Reference Polymer 1 (5 pbw)18 Comparative Example 4 Resist 2 Reference Polymer 2 (5 pbw) 2Comparative Example 5 Resist 2 Reference Polymer 3 (5 pbw) 6

In a further run, the resist solutions of Examples 1 and 13 andComparative Examples 4 and 5 were refined by three passes of filteringthrough a high-density polyethylene filter with a pore size of 0.02 μm.The resist solution was applied onto an antireflective coating ARC-29A(Nissan Chemical Co., Ltd.) of 87 nm thick formed on a 8-inch siliconsubstrate and baked at 110° C. for 60 seconds, forming a resist film of150 nm thick. The wafer over its entire surface was exposed by means ofan ArF scanner model S307E (Nikon Corp., NA 0.85, σ 0.93, ⅘ annularillumination, 6% halftone phase shift mask), post-exposure baked (PEB)at 110° C. for 60 seconds, and developed with a 2.38 wt % TMAH aqueoussolution for 30 seconds, forming a 100-nm line-and-space pattern overthe wafer surface. Using a flaw detector Win-Win 50-1200 (Tokyo SeimitsuCo., Ltd.), defects were observed at the pixel size of 0.125 μm. Theresults are shown in Table 4.

TABLE 4 Resist solution Number of defects Example 1 2 Example 13 5Comparative Example 4 143 Comparative Example 5 103EB Exposure

In an EB exposure test, a positive resist material was prepared bydissolving an EB lithographic resist polymer synthesized by radicalpolymerization, and other components, all shown below, in propyleneglycol monomethyl ether acetate (PGMEA) and ethyl lactate (EL) accordingto the recipe shown in Table 5, and filtering through a filter with apore size of 0.2 μm.

Using Clean Track Mark 5 (Tokyo Electron Ltd.), the positive resistmaterial was spin coated on a silicon substrate with a diameter of 6inches and prebaked on a hot plate at 110° C. for 60 seconds to form aresist film of 200 nm thick. Using HL-800D (Hitachi, Ltd.) at a HVvoltage of 50 keV, imagewise exposure was performed on the resist filmin a vacuum chamber. The resist film was then allowed to stand in thevacuum chamber for 20 hours, after which additional imagewise exposurewas performed at a different area.

Using Clean Track Mark 5 (Tokyo Electron Ltd.), immediately after theimagewise exposure, the resist film was post-exposure baked (PEB) on ahot plate at 90° C. for 60 seconds and puddle developed in a 2.38 wt %TMAH aqueous solution for 30 seconds to form a positive pattern. Theresist pattern was evaluated as follows.

Using a measurement SEM S-7280 (Hitachi, Ltd.), the line width of a 0.12μm line-and-space pattern at the exposure dose which provided a 1:1resolution at the top and bottom of a 0.12 μm line-and-space pattern inthe area exposed immediately before development was measured. A widthchange during vacuum holding was determined by subtracting therefrom theline width of a 0.12 μm line-and-space pattern at the same exposure dosein the area exposed 20 hours earlier. Positive values of width changeindicate that the resist sensitivity varies toward a higher level duringvacuum holding whereas negative values indicate that the resistsensitivity varies toward a lower level.

TABLE 5 Basic Dissolution Organic Additive Width Polymer PAG compoundregulator solvent polymer change (pbw) (pbw) (pbw) (pbw) (pbw) (pbw)(nm) EB resist polymer PAG2 Quencher1 — PGMEA (700) Polymer 1 −1 (100)(10) (0.4) EL (300) (5) EB resist polymer PAG2 Quencher1 — PGMEA (700)Polymer 2  0 (100) (10) (0.4) EL (300) (5) EB resist polymer PAG2Quencher1 — PGMEA (700) Polymer 3 −1 (100) (10) (0.4) EL (300) (5) EBresist polymer PAG2 Quencher1 — PGMEA (700) Polymer 4 −1 (100) (10)(0.4) EL (300) (5) EB resist polymer PAG2 Quencher1 — PGMEA (700)Polymer 5  0 (100) (10) (0.4) EL (300) (5) EB resist polymer PAG2Quencher1 — PGMEA (700) Polymer 6 −1 (100) (10) (0.4) EL (300) (5) EBresist polymer PAG2 Quencher1 — PGMEA (700) — −9 (100) (10) (0.4) EL(300) EB resist polymer PAG2 Quencher1 — PGMEA (700) Polymer 7 −1 (100)(10) (0.4) EL (300) (5)

As is evident from Table 3, the photoresist films formed from the resistsolutions having the additive polymers of the invention compoundedtherein (Examples 1 to 19) are effective for preventing the PAGcomponent from being leached out in water.

While the invention has been described with reference to a preferredembodiment, it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment disclosed as the best modecontemplated for carrying out this invention, but that the inventionwill include all embodiments falling within the scope of the appendedclaims.

Although the resist composition applied to the immersion lithography hasbeen described, it is also applicable to conventional lithography.

When a polymer of the invention is added to an EB lithography resist, itimproves the stability of a resist film during vacuum holding.

Japanese Patent Application No. 2006-282203 is incorporated herein byreference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A resist composition which is a chemically amplified positive resistcomposition, comprising 100 parts by weight of a base resin comprisingat least recurring units having acid labile groups and recurring unitshaving hydroxyl groups and/or adhesive groups of lactone ring, and 0.1to 50 parts by weight the polymer comprising recurring units of formula(1):

wherein R¹, R⁴, R⁷, and R¹⁴ are each independently hydrogen or methyl,R², R³, R¹⁵, and R¹⁶ are each independently hydrogen or a straight,branched or cyclic C₁-C₂₀ alkyl or fluoroalkyl group, or R² and R³, andR¹⁵ and R¹⁶ may bond together to form a ring with the carbon atom towhich they are attached, and in this case, R² and R³, and R¹⁵ and R¹⁶,taken together, stand for a straight, branched or cyclic C₂-C₂₀ alkyleneor fluoroalkylene group, R is fluorine or hydrogen, or may bond with R⁵to form a ring of 3 to 10 carbon atoms in total with the carbon atom towhich they are attached, R⁵ is a straight, branched or cyclic C₁-C₆alkylene group in which at least one hydrogen atom may be substituted bya fluorine atom, R⁶ is a straight or branched C₁-C₁₀ alkyl group inwhich at least one hydrogen atom is substituted by a fluorine atom, R⁵and R⁶ may bond together to form a ring with the carbon atoms to whichthey are attached, and in this case, R⁵ and R⁶, taken together, standfor a trivalent organic group of 2 to 12 carbon atoms in total in whichat least one hydrogen atom is substituted by a fluorine atom, R⁸ is asingle bond or a C₁-C₄ alkylene group, R¹⁰ and R¹¹ are eachindependently hydrogen, fluorine, methyl or trifluoromethyl, R¹² and R¹³are each independently a single bond, —O— or —CR¹⁸R¹⁹—, R⁹, R¹⁸, and R¹⁹are hydrogen, fluorine, methyl or trifluoromethyl, R¹⁷ is a straight orbranched C₁-C₄ alkylene group or may bond with R¹⁵ or R¹⁶ to form aC₃-C₁₀ aliphatic ring with the carbon atom to which they are attached,X¹, X² and X³ are each independently —C(═O)—O—, —O—, or—C(═O)—R²⁰—C(═O)—O— wherein R²⁰ is a straight, branched or cyclic C₁-C₁₀alkylene group, the subscripts are numbers in the range: 0≦(a-1)<1,0≦(a-2)<1, 0≦(a-3)<1, 0<(a-1)+(a-2)+(a-3)<1, 0<b<1, and0<(a-1)+(a-2)+(a-3)+b≦1.
 2. The resist composition of claim 1, furthercomprising at least one member selected from the group consisting of anorganic solvent, a basic compound, a dissolution regulator, acrosslinker, and a surfactant.
 3. A pattern forming process comprisingthe steps of: applying the resist composition of claim 1 onto asubstrate to form a coating, heat treating the coating and exposing itto high-energy radiation, and developing the exposed coating with adeveloper.
 4. The process of claim 3, wherein the high-energy radiationhas a wavelength of 180 to 250 nm.
 5. The process of claim 3, whereinthe exposing step is by immersion lithography involving exposing thecoating to high-energy radiation through a liquid.
 6. The process ofclaim 5, wherein the immersion lithography involves using high-energyradiation having a wavelength of 180 to 250 nm, introducing a liquidbetween the resist-coated substrate and a projection lens, and exposingthe substrate to the high-energy radiation through the liquid.
 7. Theprocess of claim 5, wherein the liquid is water.
 8. The process of claim3, wherein the high-energy radiation is an electron beam.
 9. A patternforming process comprising the steps of: applying the resist compositionof claim 1 onto a mask blank substrate to form a coating, heat treatingthe coating and exposing it to high-energy radiation, and developing thecoating with a developer.
 10. The resist composition of claim 1, whereinthe recurring units (a-1) in formula (1) are selected from the groupconsisting of the following formulae:

wherein R¹ is each independently hydrogen or methyl, the recurring units(a-2) in formula (I) are selected from the group consisting of thefollowing formulae:

wherein R⁴ is each independently hydrogen or methyl, the recurring units(a-3) in formula (I) are selected from the group consisting of thefollowing formulae:

wherein R⁷ is each independently hydrogen or methyl, and the recurringunits (b) in formula (I) are selected from the group consisting of thefollowing formulae:

wherein R¹⁴ is each independently hydrogen or methyl.
 11. A patternforming process comprising the steps of: applying a resist compositionof claim 1 onto a substrate to form a coating, heat treating the coatingand exposing it to an electron beam, and developing the exposed coatingwith a developer, said resist composition comprising a polymercomprising recurring units having the general formula (1):

wherein R¹, R⁴, R⁷, and R¹⁴ are each independently hydrogen or methyl,R², R³, R¹⁵, and R¹⁶ are each independently hydrogen or a straight,branched or cyclic C₁-C₂₀ alkyl or fluoroalkyl group, or R² and R³, andR¹⁵ and R¹⁶ may bond together to form a ring with the carbon atom towhich they are attached, and in this case, R² and R³, and R¹⁵ and R¹⁶,taken together, stand for a straight, branched or cyclic C₂-C₂₀ alkyleneor fluoroalkylene group, R is fluorine or hydrogen, or may bond with R⁵to form a ring of 3 to 10 carbon atoms in total with the carbon atom towhich they are attached, R⁵ is a straight, branched or cyclic C₁-C₆alkylene group in which at least one hydrogen atom may be substituted bya fluorine atom, R⁶ is a straight or branched C₁-C₁₀ alkyl group inwhich at least one hydrogen atom is substituted by a fluorine atom, R⁵and R⁶ may bond together to form a ring with the carbon atoms to whichthey are attached, and in this case, R⁵ and R⁶, taken together, standfor a trivalent organic group of 2 to 12 carbon atoms in total in whichat least one hydrogen atom is substituted by a fluorine atom, R⁸ is asingle bond or a C₁-C₄ alkylene group, R¹⁰ and R¹¹ are eachindependently hydrogen, fluorine, methyl or trifluoromethyl, R¹² and R¹³are each independently a single bond, —O— or —CR¹⁸R¹⁹—, R⁹, R¹⁸, and R¹⁹are hydrogen, fluorine, methyl or trifluoromethyl, R¹⁷ is a straight orbranched C₁-C₄ alkylene group or may bond with R¹⁵ or R¹⁶ to form aC₃-C₁₀ aliphatic ring with the carbon atom to which they are attached,X¹, X² and X³ are each independently —C(═O)—O—, —O—, or—C(═O)—R²⁰—C(═O)—O— wherein R²⁰ is a straight, branched or cyclic C₁-C₁₀alkylene group, the subscripts are numbers in the range: 0≦(a-1)<1,0≦(a-2)<1, 0≦(a-3)<1, 0<(a-1)+(a-2)+(a-3)<1, 0<b<1, and0<(a-1)+(a-2)+(a-3)+b≦1.
 12. A resist composition which is a chemicallyamplified negative resist composition, comprising a polymer comprisingrecurring units having the general formula (1):

wherein R¹, R⁴, R⁷, and R¹⁴ are each independently hydrogen or methyl,R², R³, R¹⁵, and R¹⁶ are each independently hydrogen or a straight,branched or cyclic C₁-C₂₀ alkyl or fluoroalkyl group, or R² and R³, andR¹⁵ and R¹⁶ may bond together to form a ring with the carbon atom towhich they are attached, and in this case, R² and R³, and R¹⁵ and R¹⁶,taken together, stand for a straight, branched or cyclic C₂-C₂₀ alkyleneor fluoroalkylene group, R is fluorine or hydrogen, or may bond with R⁵to form a ring of 3 to 10 carbon atoms in total with the carbon atom towhich they are attached, R⁵ is a straight, branched or cyclic C₁-C₆alkylene group in which at least one hydrogen atom may be substituted bya fluorine atom, R⁶ is a straight or branched C₁-C₁₀ alkyl group inwhich at least one hydrogen atom is substituted by a fluorine atom, R⁵and R⁶ may bond together to form a ring with the carbon atoms to whichthey are attached, and in this case, R⁵ and R⁶, taken together, standfor a trivalent organic group of 2 to 12 carbon atoms in total in whichat least one hydrogen atom is substituted by a fluorine atom, R⁸ is asingle bond or a C₁-C₄ alkylene group, R¹⁰ and R¹¹ are eachindependently hydrogen, fluorine, methyl or trifluoromethyl, R¹² and R¹³are each independently a single bond, —O— or —CR¹⁸R¹⁹—, R⁹, R¹⁸, and R¹⁹are hydrogen, fluorine, methyl or trifluoromethyl, R¹⁷ is a straight orbranched C₁-C₄ alkylene group or may bond with R¹⁵ or R¹⁶ to form aC₃-C₁₀ aliphatic ring with the carbon atom to which they are attached,X¹, X² and X³ are each independently —C(═O)—O—, —O—, or—C(═O)—R²⁰—C(═O)—O— wherein R²⁰ is a straight, branched or cyclic C₁-C₁₀alkylene group, the subscripts are numbers in the range: 0≦(a-1)<1,0≦(a-2)<1, 0≦(a-3)<1, 0<(a-1)+(a-2)+(a-3)<1, 0<b<1, and0<(a-1)+(a-2)+(a-3)+b≦1.
 13. The resist composition of claim 12, furthercomprising at least one member selected from the group consisting of anorganic solvent, a basic compound, a crosslinker, and a surfactant. 14.A pattern forming process comprising the steps of: applying the resistcomposition of claim 12 onto a substrate to form a coating, heattreating the coating and exposing it to high-energy radiation, anddeveloping the exposed coating with a developer.
 15. The process ofclaim 14, wherein the exposing step is by immersion lithographyinvolving exposing the coating to high-energy radiation through aliquid, wherein the immersion lithography involves using high-energyradiation having a wavelength of 180 to 250 nm, introducing a liquidbetween the resist-coated substrate and a projection lens, and exposingthe substrate to the high-energy radiation through the liquid.
 16. Theprocess of claim 15, wherein the liquid is water.
 17. The process ofclaim 14, wherein the high-energy radiation is an electron beam.
 18. Apattern forming process comprising the steps of: applying the resistcomposition of claim 12 onto a mask blank substrate to form a coating,heat treating the coating and exposing it to high-energy radiation, anddeveloping the coating with a developer.